Android学习笔记-Android初级 (一)

1.Activity屏幕方向与显示方式与屏幕旋转

//代码设置横竖屏，也可以在menifest中设置
//setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);//横屏
//setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);//竖屏

<activity android:name=".TimeActivity" android:theme="@android:style/Theme.NoTitleBar.Fullscreen" />
<activity android:name=".MenuActivity" android:screenOrientation="landscape" />

//去掉标题栏和通知栏，在setContentview之前设置
//设置全屏模式
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
//去除标题栏
requestWindowFeature(Window.FEATURE_NO_TITLE);
//activity窗口化运行
".TextSwitcherActivity" android:theme="@android:style/Theme.Dialog" />

//屏幕旋转的时候，执行了onCreate，说明activity被重建了，所以在屏幕旋转时候，要保存状态，在旋转之后再把数据恢复
//屏幕旋转时会触发（也就是说异常销毁activity）
protected void onSaveInstanceState(Bundle outState) {
   super.onSaveInstanceState(outState);
   outState.putString("key1","valuess");
}
//可以在onCreate中恢复数据
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if(savedInstanceState !=null) {
     String str =    savedInstanceState.getString("key1");
    }
    setContentView(R.layout.activity_time);

}
//可以在onCreate中恢复数据,也可以在onRestoreInstanceState中恢复数据


@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
}

//也可以旋转屏幕的时候，不让它重新创建
".TextSwitcherActivity" 
android:configChanges="keyboard|screenSize|orientation" />//加上这个属性后，旋转屏幕的时候不会重新创建，会调用onContentChanged这个方法这个方法一般不用做什么操作
public void onContentChanged() {
    super.onContentChanged();
}

2.SharedPreferences 在onPause中保存，在onResume中恢复数据

package com.recycler.zx.zxrecyclerview;

import android.content.Context;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class SharePreferenceActivity extends AppCompatActivity {

    private SharedPreferences sf;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_share_preference);
        //获取当前程序SharedPreferences
        sf = getSharedPreferences("share_all", Context.MODE_PRIVATE);
    }

    //进行还原数据
    @Override
    protected void onResume() {
        super.onResume();

       String result =  sf.getString("key1","");
    }

    //在该时间方法里来存储数据
    @Override
    protected void onPause() {
        super.onPause();

        SharedPreferences.Editor editor =  sf.edit();
        editor.putString("key1","values1");
        editor.commit();

        editor.remove("key1");//根据key删除
        editor.clear();//清楚所有的SharedPreferences
    }
}

3.Intent

//直接查找法（通过组件名称）
Intent intent = new Intent();
ComponentName componentName = new ComponentName(this,MenuActivity.class);
intent.setComponent(componentName);
/用的最多的//用的最多的
Intent intent = new Intent();
intent.setClass(this,MenuActivity.class);
startActivity(intent);

4.创建服务service

android studio 可以直接右键创建一个service，（会自动在menifest中注册）

<service
    android:name=".Service.MyService"
    android:enabled="true"
    android:exported="true">service>

5.广播

开启启动广播，先自动创建一个
StartupReceiver
".BroadcastReceiver.SystemBroadcast.StartupReceiver"
    android:enabled="true"
    android:exported="true">

    
        "android.intent.action.BOOT_COMPLETED">
    


"android.permission.RECEIVE_BOOT_COMPLETED" />

检测网络状态：
package com.recycler.zx.zxrecyclerview.BroadcastReceiver.SystemBroadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.widget.Toast;

public class InternetReceiver extends BroadcastReceiver {
    public InternetReceiver() {
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = manager.getActiveNetworkInfo();
        if(info !=null) {
            String name = info.getType()+"";
            Toast.makeText(context,"---"+name,Toast.LENGTH_SHORT).show();
        }

    }
}

6.fragment的两种添加方式

//xml文件添加
package com.recycler.zx.zxrecyclerview.fragments;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.recycler.zx.zxrecyclerview.R;

public class FragmentsActivity extends AppCompatActivity {


    TitleFragment titleFragment;
    ContentFragment contentFragment;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragments);
        titleFragment = (TitleFragment) getFragmentManager().findFragmentById(R.id.fragment_title);
        contentFragment = (ContentFragment) getFragmentManager().findFragmentById(R.id.fragment_content);
    }
}

"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context="com.recycler.zx.zxrecyclerview.fragments.FragmentsActivity">


"0dp"
    android:id="@+id/fragment_title"
    android:layout_weight="1"
    android:name="com.recycler.zx.zxrecyclerview.fragments.TitleFragment"
    android:layout_height="match_parent"/>
"@+id/fragment_content"
    android:layout_width="0dp"
    android:layout_weight="3"
    android:name="com.recycler.zx.zxrecyclerview.fragments.ContentFragment"

    android:layout_height="match_parent"/>


//fragment可以直接右键新建
package com.recycler.zx.zxrecyclerview.fragments;

import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.recycler.zx.zxrecyclerview.R;

/**
 * Created by zx on 2015/12/17.
 */
public class TitleFragment extends Fragment {


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v= inflater.inflate(R.layout.layout_title,container,false);
        return v;
    }
}

package com.recycler.zx.zxrecyclerview.fragments;

import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.recycler.zx.zxrecyclerview.R;

/**
 * Created by zx on 2015/12/17.
 */
public class ContentFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v= inflater.inflate(R.layout.layout_content,container,false);
        return v;
    }
}

//代码添加

package com.recycler.zx.zxrecyclerview.fragments;

import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.recycler.zx.zxrecyclerview.R;

public class FragmentsCodeActivity extends AppCompatActivity {

    ContentFragment contentFragment;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragments_code);

        addContentLayout();
    }

    //t通过代码添加fragment
    private void addContentLayout() {
        FragmentManager fm =  getFragmentManager();
        //开启一个事务
        FragmentTransaction ft = fm.beginTransaction();
        contentFragment = new ContentFragment();

        //添加fragment
        ft.add(R.id.frameLayout_content,contentFragment);
        //ft.remove();
       // ft.replace();替换，先删除，再添加
        ft.commit();//提交事务
    }
}

"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.recycler.zx.zxrecyclerview.fragments.FragmentsCodeActivity">


    "0dp"
        android:id="@+id/fragment_title"
        android:layout_weight="1"
        android:name="com.recycler.zx.zxrecyclerview.fragments.TitleFragment"
        android:layout_height="match_parent"/>
    "@+id/frameLayout_content"
        android:layout_width="0dp"
        android:layout_weight="3"
        android:layout_height="match_parent"/>

7.Fragment出入栈操作和 官方推荐传递参方法

package com.recycler.zx.zxrecyclerview.fragments;

import android.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;

import com.recycler.zx.zxrecyclerview.R;

public class PopBackTaskActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pop_back_task);
    }

    public void one(View v){
        PopBacksFragment popBacksFragment = PopBacksFragment.getInstance("one");
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.replace(R.id.ft_content,popBacksFragment);
        //把当前fragment添加到Activity栈
        ft.addToBackStack(null);
        ft.commit();

    }
    public void two(View v){
        PopBacksFragment popBacksFragment = PopBacksFragment.getInstance("two");
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.replace(R.id.ft_content,popBacksFragment);
        //把当前fragment添加到Activity栈
        ft.addToBackStack(null);
        ft.commit();
    }

    //点返回键的时候，判断栈中是否存在，存在就做出栈操作
    //比activity性能要高一些
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK) {
            //如果返回栈里面没有了
            if(getFragmentManager().getBackStackEntryCount() == 0) {
                finish();
            } else {
                getFragmentManager().popBackStack();//出栈，不进行退出操作
            }
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }
}

"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.recycler.zx.zxrecyclerview.fragments.PopBackTaskActivity">


    "wrap_content"
        android:layout_height="wrap_content"
        android:text="one"
        android:onClick="one"
        android:id="@+id/button2"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    "wrap_content"
        android:layout_height="wrap_content"
        android:text="two"
        android:onClick="two"
        android:id="@+id/button3"
        android:layout_alignParentTop="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

    "@+id/ft_content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/button2">


package com.recycler.zx.zxrecyclerview.fragments;


import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.recycler.zx.zxrecyclerview.R;

/**
 * A simple {@link Fragment} subclass.
 */
public class PopBacksFragment extends Fragment {

private static final String TITLE = "title";
    private String title ;
    public PopBacksFragment(){}
//    public PopBacksFragment(String title) {
//        this.title =title;
//    }
    //fragment的标准传参数方法,这样传参数的时候屏幕旋转数据不会消失，（并且Fragment是不允许使用有参的构造方法的）
    public static PopBacksFragment getInstance(String title){
        PopBacksFragment pf = new PopBacksFragment();
        Bundle bundle = new Bundle();
        bundle.putString(TITLE,title);
        pf.setArguments(bundle);
        return pf;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.fragment_pop_backs, container, false);
       TextView tvPop = (TextView) v.findViewById(R.id.tv_pop);
        tvPop.setText(getArguments().getString(TITLE));
        return v;
    }

}

8.fragment和activity交换数据

//把数据从MenuFragment 传递到 MainFragment

package com.recycler.zx.zxrecyclerview.fragments.fragmentAndActivity;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.recycler.zx.zxrecyclerview.R;

public class FramentAndActivity extends AppCompatActivity implements MenuFragment.MyMenuListener {

    private MenuFragment menuFragment;
    private MainFragment mainFragment;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_frament_and);
        menuFragment = (MenuFragment) getFragmentManager().findFragmentById(R.id.menu_fragment);
        mainFragment = (MainFragment) getFragmentManager().findFragmentById(R.id.main_frament);
    }

    @Override
    public void changeValue(String value) {
        mainFragment.setTvValue(value);

    }
}

package com.recycler.zx.zxrecyclerview.fragments.fragmentAndActivity;


import android.app.Activity;
import android.app.Fragment;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

import com.recycler.zx.zxrecyclerview.R;

/**
 * A simple {@link Fragment} subclass.
 */
public class MenuFragment extends Fragment {


    private MyMenuListener mMyMenuListener;
    public MenuFragment() {
        // Required empty public constructor
    }

    @Override
    public void onAttach(Activity context) {
        super.onAttach(context);
        mMyMenuListener = (MyMenuListener) context;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v =  inflater.inflate(R.layout.fragment_menu, container, false);
       Button news = (Button) v.findViewById(R.id.news);
       Button music = (Button) v.findViewById(R.id.music);
        news.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mMyMenuListener.changeValue("news");
            }
        });
        music.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mMyMenuListener.changeValue("music");
            }
        });
        return v;
    }

    //定义一个回调接口，要求宿主（包含它的Activity）去实现它
    public static interface MyMenuListener{
        public void changeValue(String value);
    }
}

package com.recycler.zx.zxrecyclerview.fragments.fragmentAndActivity;


import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.recycler.zx.zxrecyclerview.R;

import butterknife.Bind;
import butterknife.ButterKnife;

/**
 * A simple {@link Fragment} subclass.
 */
public class MainFragment extends Fragment {


    @Bind(R.id.tv_value)
    TextView tvValue;

    public MainFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_main, container, false);
        ButterKnife.bind(this, view);
        return view;
    }

    public void setTvValue(String value){
        tvValue.setText(value);
    }
    @Override
    public void onDestroyView() {
        super.onDestroyView();
        ButterKnife.unbind(this);
    }
}

8.PreferenceFragment 实现设置用户习惯操作

1.res根目录新建一个xml文件夹和xml文件

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory
        android:title="声音设置">

        <CheckBoxPreference
            android:key="checkbox_preference"
            android:title="是否打开声音"
            android:summary="打开声音后可以自动开启音乐" />

    PreferenceCategory>

    <PreferenceCategory
        android:title="城市">

        <EditTextPreference
            android:key="edittext_preference"
            android:title="昵称"
            android:summary="请输入昵称："
            android:dialogTitle="昵称哇：" />

        <ListPreference
            android:key="list_preference"
            android:title="城市名称"
            android:summary="请选择城市"
            android:entries="@array/city"
            android:entryValues="@array/city"
            android:dialogTitle="城市名称哇：" />
        <PreferenceScreen
            android:title="百度"
            android:summary="访问">

            <intent android:action="android.intent.action.VIEW"
                android:data="http://www.android.com" />

        PreferenceScreen>
    PreferenceCategory>

PreferenceScreen>

2.String.xml中可能需要使用
 <string-array name="city">
        <item>北京item>
        <item>上海item>
        <item>关注item>
        <item>杭州item>
    string-array>
resources>

3. PrefsFragmentextends PreferenceFragment 
package com.recycler.zx.zxrecyclerview.fragments.preference;

import android.os.Bundle;
import android.preference.PreferenceFragment;

import com.recycler.zx.zxrecyclerview.R;

public class PrefsFragment extends PreferenceFragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Load the preferences from an XML resource
        addPreferencesFromResource(R.xml.my_preference);
    }
}

9.ActionBar

package com.recycler.zx.zxrecyclerview.ActionBar;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.MenuItemCompat;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.SearchView;
import android.support.v7.widget.ShareActionProvider;
import android.telephony.PhoneStateListener;
import android.telephony.TelephonyManager;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import com.recycler.zx.zxrecyclerview.MenuActivity;
import com.recycler.zx.zxrecyclerview.R;
import com.recycler.zx.zxrecyclerview.TimeActivity;
import com.recycler.zx.zxrecyclerview.fragments.ContentFragment;
import com.recycler.zx.zxrecyclerview.fragments.TitleFragment;

public class MyActionBarActivity extends AppCompatActivity implements ActionBar.TabListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_action_bar);
        ActionBar actionBar = getSupportActionBar();
//        actionBar.hide();//隐藏actionbar
        actionBar.setHomeButtonEnabled(true);
        startActivity(new Intent(this, MenuActivity.class));

        //导航条
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        actionBar.setDisplayShowTitleEnabled(false);//标题栏不显示
        //添加选项卡
        ActionBar.Tab tab = actionBar.newTab()
                .setText("美女")
                .setTabListener(this);
        actionBar.addTab(tab);

        tab = actionBar.newTab()
                .setText("新闻")
                .setTabListener(this);
        actionBar.addTab(tab);

        TelephonyManager telephonyManager = (TelephonyManager)getSystemService(Context.TELEPHONY_SERVICE);
        telephonyManager.getCallState();
        telephonyManager.listen(new PhoneStateListener(),PhoneStateListener.LISTEN_CALL_STATE );
    }

    @Override
    public boolean onCreateOptionsMenu( Menu menu) {
        getMenuInflater().inflate(R.menu.menu_context, menu);
        //搜索
        MenuItem mi = menu.findItem(R.id.yellow);
        SearchView searchView = (SearchView) MenuItemCompat.getActionView(mi);
        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                Toast.makeText(MyActionBarActivity.this,"---"+query,Toast.LENGTH_SHORT).show();
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                return false;
            }


        });
        //分享
        MenuItem mi2 =  menu.findItem(R.id.share);
        ShareActionProvider provier = (ShareActionProvider)MenuItemCompat.getActionProvider(mi2);
        provier.setShareIntent(getDefaultIntent2());
        return true;

    }
    private Intent getDefaultIntent(){
        Intent in = new Intent(Intent.ACTION_SEND);
        in.setType("image/*");
        return in;
    }
    private Intent getDefaultIntent2(){
        Intent intent = new Intent(Intent.ACTION_SEND);
        intent.setType("text/plain");
        intent.putExtra(Intent.EXTRA_TEXT,"这是。。");
        startActivity(intent);
        return intent;
    }

    //导航条
    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
    Toast.makeText(this,tab.getText(),Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {

    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {

    }


    //电话服务
    class PhoneStateListener extends android.telephony.PhoneStateListener{
        @Override
        public void onCallStateChanged(int state, String incomingNumber) {
            super.onCallStateChanged(state, incomingNumber);

            switch (state) {
                case TelephonyManager.CALL_STATE_RINGING :
                    Toast.makeText(MyActionBarActivity.this,"正在响铃",Toast.LENGTH_SHORT).show();
                    break;
                case TelephonyManager.CALL_STATE_IDLE :
                    Toast.makeText(MyActionBarActivity.this,"正在响铃",Toast.LENGTH_SHORT).show();
                    break;
                case TelephonyManager.CALL_STATE_OFFHOOK :
                    Toast.makeText(MyActionBarActivity.this,"正在响铃",Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }
}

"http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.recycler.zx.zxrecyclerview.MainActivity" >
    
    "@+id/red"
        android:title="红色"
        android:orderInCategory="100"
        app:showAsAction="ifRoom|withText"
         />
    "@+id/blue"
        android:title="蓝色"
        app:showAsAction="ifRoom|collapseActionView"
        android:orderInCategory="200"
         />
    "@+id/yellow"
        android:title="搜索"
        android:icon="@android:drawable/ic_menu_search"
        app:showAsAction="ifRoom|collapseActionView"
        app:actionViewClass="android.support.v7.widget.SearchView"
        android:orderInCategory="300"
         />
    
    "@+id/share"
        android:title="分享"
        android:icon="@android:drawable/ic_menu_share"
        app:showAsAction="ifRoom"
        android:orderInCategory="400"
        app:actionProviderClass="android.support.v7.widget.ShareActionProvider"
         />


public class MenuActivity extends AppCompatActivity {

    @Bind(R.id.tv_bg)
    TextView mTvBg;
    @Bind(R.id.tv_popmenu)
    TextView mTvPopmenu;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu);
        ButterKnife.bind(this);
        ActionBar actionBar = getSupportActionBar();
//        actionBar.hide();//隐藏actionbar
        actionBar.setDisplayHomeAsUpEnabled(true);//设置当前的activity

10.handler实现原理与机制

1.handler发送一个消息（Message）到消息队列（MessageQueue）
2.Looper检查消息队列（MessageQueue先进先出）中是否有消息
3.如果检测到MessageQueue有消息就发送消息（1.obtainMessage2.msg.obj = “1”3.sendMessage）到HandlerMessage把消息传递回去

Message msg = new Message();
Message msg = obtainMessage();//使用消息池，消息对象复用，不用每次都new（消息对象池的机制：链表结构）

//handler机制：
1.Message 消息对象，内部使用链表数据结构实现一个消息池，用于复用，避免大量创建消息对象，造成内存浪费
2.Handler 消息处理者，通过该对象把消息存入消息队列，并通过handlerMessage方法处理消息
3.MessageQueue消息队列，用于存储Message对象的数据结构，先进先出
4.Looper消息队列的处理者，用于循环检测消息队列（MessageQueue），从消息队列中一个一个的取出消息对象，传入HandlerMessage方法中

11.Handler内存泄露分析

package com.recycler.zx.zxrecyclerview.Handler;

import android.app.Activity;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

import com.recycler.zx.zxrecyclerview.R;

import java.lang.ref.WeakReference;

//Handler的内存泄露问题
//1.定义一个内部类时，会默认拥有外部类对象的引用,所以建议使用内部类时，最好定义一个静态（static）内部类（因为静态内部类就相当于一个外部类，不拥有外部类的引用）
//2.引用的强弱：强引用(new 出来的对象，就是强引用，就算内存不足也不会被自动回收,想要回收必须把对象置空或销毁当前对象，回收器才会回收)
// ->软引用（A引用B，当B内存不足的时候，系统就会回收它）
// ->弱引用（引用的对象如果不存在就得不到）
//3.
public class MemoryOverflowActivity extends AppCompatActivity {

    private String name;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_memory_overflow);
        //这样写会出现内存泄露
        /*1.当Handler作为内部类使用的时候，那么handler持有外部类的引用；
        如果外部类退出的时候，handler还在运行的话，外部类（Activity）就退出不了，就算退出了，还还在占用着内存。那么就造成了内存溢出（泄露）
        （Handler依赖于外部类）*/
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {

            }
        },60*10*1000);//延迟10分钟执行run方法
        Toast.makeText(this,"来过",Toast.LENGTH_SHORT).show();
        finish();
    }

    private MyHandler handler = new MyHandler(this);





    //这个是标准的Handler写法，1.static内部类（相当于外部类，不依赖外部类）2.弱引用（防止内存泄露）3.通过mWeakReference.get()返回一个Activity
    private  static class MyHandler extends Handler{
        //软引用Activity
        WeakReference mWeakReference;
        public MyHandler(MemoryOverflowActivity activity){
            mWeakReference = new WeakReference(activity);
        }
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            //如果MemoryOverflowActivity被销毁了，那么mWeakReference.get()返回的就是null
            //如果返回null你就不能 name 变量（因为name属于MemoryOverflowActivity的变量，MemoryOverflowActivity为null，它的变量自然就不能使用）
            //使用弱引用，就可以避免内存泄露（溢出）
            MemoryOverflowActivity activity =  mWeakReference.get();
            if(activity != null) {

            }
        }
    }
}

SplashAcitivity的Style
".FirstActivity"  android:theme="@android:style/Theme.DeviceDefault.Light.NoA

12.执行耗时操作的第二种方式（AsyncTask），第一种是Thread

package com.recycler.zx.zxrecyclerview.Handler;

import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import com.recycler.zx.zxrecyclerview.R;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import javax.net.ssl.HttpsURLConnection;

import butterknife.Bind;
import butterknife.ButterKnife;

//Handler的内存泄露问题
//1.定义一个内部类时，会默认拥有外部类对象的引用,所以建议使用内部类时，最好定义一个静态（static）内部类（因为静态内部类就相当于一个外部类，不拥有外部类的引用）
//2.引用的强弱：强引用(new 出来的对象，就是强引用，就算内存不足也不会被自动回收,想要回收必须把对象置空或销毁当前对象，回收器才会回收)
// ->软引用（A引用B，当B内存不足的时候，系统就会回收它）
// ->弱引用（引用的对象如果不存在就得不到）
//3.
public class MemoryOverflowActivity extends AppCompatActivity {

    @Bind(R.id.textView2)
    TextView textView2;
    @Bind(R.id.progressBar2)
    ProgressBar progressBar2;
    private String name;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_memory_overflow);
        ButterKnife.bind(this);
        //这样写会出现内存泄露
        /*1.当Handler作为内部类使用的时候，那么handler持有外部类的引用；
        如果外部类退出的时候，handler还在运行的话，外部类（Activity）就退出不了，就算退出了，还还在占用着内存。那么就造成了内存溢出（泄露）
        （Handler依赖于外部类）*/
        /*new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {

            }
        }, 60 * 10 * 1000);//延迟10分钟执行run方法
        Toast.makeText(this, "来过", Toast.LENGTH_SHORT).show();
        finish();*/
    }

    private MyHandler handler = new MyHandler(this);


    //这个是标准的Handler写法，1.static内部类（相当于外部类，不依赖外部类）2.软引用（防止内存泄露）3.通过mWeakReference.get()返回一个Activity
    private static class MyHandler extends Handler {
        //软引用Activity
        WeakReference mWeakReference;

        public MyHandler(MemoryOverflowActivity activity) {
            mWeakReference = new WeakReference(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            //如果MemoryOverflowActivity被销毁了，那么mWeakReference.get()返回的就是null
            //如果返回null你就不能 name 变量（因为name属于MemoryOverflowActivity的变量，MemoryOverflowActivity为null，它的变量自然就不能使用）
            //使用软引用，就可以避免内存泄露（溢出）
            MemoryOverflowActivity activity = mWeakReference.get();
            if (activity != null) {

            }
        }
    }


    //通过AsyncTask实现一个异步任务
    private static class DownLoadAsynTask extends AsyncTask<String, Integer, String> {

        private MemoryOverflowActivity mActivity;//这样写是有问题的，你既然使用了弱引用，就不能申明成员变量
在下面的每个方法中，只要你用到了你就必须通过mWeakReference.get();方法获取，不能直接申明一个成员变量接收

        public DownLoadAsynTask(MemoryOverflowActivity activity) {
            WeakReference mWeakReference = new WeakReference(activity);
            mActivity = mWeakReference.get();
        }
        //执行任务之前触发，可以做一些初始化工作,主线程调用的

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mActivity.textView2.setText("开始执行下载任务");
            mActivity.progressBar2.setProgress(0);
        }

        //执行后台任务的方法，类似于线程，所以不能在该方法中访问Ui组件
        @Override
        protected String doInBackground(String... params) {
            String imgurl = params[0];
            try {
                URL url = new URL(imgurl);
                //打开连接
                HttpURLConnection con = (HttpURLConnection) url.openConnection();
                int size = con.getContentLength();
                //0:表示需要更新最大进度值1：表示更新当前进度值
                publishProgress(0,size);
                InputStream in = con.getInputStream();

                byte[] bytes = new byte[20];
                int len = -1;
                while((len = in.read(bytes)) != -1) {
                    //out.write(bytes,0,size);
                    publishProgress(1,len);//更新当前进度
                    //out.flush();
                }
                //out.close();
                in.close();
            } catch (Exception e) {
                e.printStackTrace();
                return "error";
            }
            return "success";

        }

        //更新进度值
        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
            switch (values[0]){
                case 0:
                mActivity.progressBar2.setMax(values[1]);
                    break;
                case 1:
                    mActivity.progressBar2.incrementProgressBy(values[1]);
                    break;
            }
        }

        //当doInBackground被调用返回的时候调用
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            if(s.equals("success")) {
                mActivity.textView2.setText("下载完成");
            }else {
                Toast.makeText(mActivity,"失败",Toast.LENGTH_SHORT).show();
            }
        }
    }

    public void download(View v) {
        DownLoadAsynTask task = new DownLoadAsynTask(this);
        task.execute("http://p2.so.qhimg.com/t01e767afd2dbff19ac.jpg");
    }

}

"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.recycler.zx.zxrecyclerview.Handler.MemoryOverflowActivity">


    "wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Large Text"
        android:id="@+id/textView2"
        android:onClick="download"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    "?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/progressBar2"
        android:layout_below="@+id/textView2"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

13.文件管理

package com.recycler.zx.zxrecyclerview.FileReadWriter;

import android.content.Context;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

import com.recycler.zx.zxrecyclerview.R;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;

public class FileActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_file);
        try {
            //存储私有文件
            savePrivateFile();
            //读取私有文件
            readPrivateFile();
            //读取res/raw
            readRawFile();
            //读取缓存文件
            readCacheFile();
            //sd卡管理：写入
            writeToSDcard();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //判断有sd卡，并且不是只读的
    private boolean isExternalStorageWritable(){
        String state = Environment.getExternalStorageState();
        if(Environment.MEDIA_MOUNTED.equals(state)){//是否有sd卡
            //判断是不是只读的sd卡
            if(!state.equals(Environment.MEDIA_MOUNTED_READ_ONLY)) {

                return true;
            }
            return false;
        }
        return false;
    }
    private void writeToSDcard() {
        if(isExternalStorageWritable()) {
        //访问sd卡路径
        Environment.getExternalStorageDirectory().getPath();
        //可以访问和保存不同类型的 storage/sdcard/movies丶storage/sdcard/pictures
        Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MOVIES);
        Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MUSIC);
        }
    }
    //写入外部（sd卡）私有文件
    private void writePrivateToSDcard() {
        //别的程序无法访问
        //getExternalFilesDir在手机把内部存储当做外部sd卡存储使用的时候此方法返回null
        //storage/sdcard/android/data/com.recycler.zx.zxrecyclerview/1.txt
        File file = getExternalFilesDir(null);
        if(file != null) {
            try {
                FileOutputStream out = new FileOutputStream(file+"/1.txt");
                PrintStream ps = new PrintStream(out);
                ps.print("1111111111111");
                ps.close();
                out.close();
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }
    //写入缓存到外部sd卡
    private void writeCacheFileToSDcard() {
        //别的程序无法访问
        //getExternalFilesDir在手机把内部存储当做外部sd卡存储使用的时候此方法返回null
        //storage/sdcard/android/data/com.recycler.zx.zxrecyclerview/1.txt
        try {
        File file = File.createTempFile("sss",null,getExternalCacheDir());
        if(file != null) {

                FileOutputStream out = new FileOutputStream(file+"/1.txt");
                PrintStream ps = new PrintStream(out);
                ps.print("1111111111111");
                ps.close();
                out.close();
        }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void readCacheFile() {
        try {
            File file = File.createTempFile("temp.tmp",null,getCacheDir());
            FileOutputStream out = new FileOutputStream(file);
            PrintStream ps = new PrintStream(out);
            ps.print("星星是");

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void readRawFile() {
        try{
            InputStream is = getResources().openRawResource(R.raw.a);
            StringBuffer sb2 = new StringBuffer();
            byte[] bs2 = new byte[1024];
            int len2 = -1;
            while((len2 = is.read(bs2))!=-1) {
                sb2.append(new String(bs2,0,bs2.length));
            }
            is.close();
            Toast.makeText(this,sb2,Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void readPrivateFile() {
        try{
            InputStream in = openFileInput("a.txt");
            StringBuffer sb = new StringBuffer();
            byte[] bs = new byte[1024];
            int len = -1;
            while((len = in.read(bs))!=-1) {
                sb.append(new String(bs,0,bs.length));
            }
            in.close();
            Toast.makeText(this,sb,Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void savePrivateFile() {
        try{
        OutputStream out = openFileOutput("a.txt", Context.MODE_APPEND);//MODE_PRIVATE代表覆盖,MODE_APPEND代表追加
        String info = "1111";
        byte[] bytes = info.getBytes();
        out.write(bytes,0,bytes.length);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

14.json和xml比较

15.Gson解析数据

总结：
1.凡是遇到 {} 就用对象解析
public MyWeather parseJsonArrayFromGsons2(){
String weatherList = readAssertFile(“cache/Weather.json”);
Gson gson = new Gson();
return gson.fromJson(weatherList, MyWeather.class);
}
遇到：[] 就用数组解析
public List parseJsonArrayFromGsons(){
String citylist = readAssertFile(“cache/StoreTypeList.json”);
Type type = new TypeToken