Android应用组件Activity
一、Activity简介
1、Activity拥有可以编辑用户界面的窗口，窗口布满整个屏幕，也可以小于或者漂浮于其他窗口之上
2、应用程序通常拥有多个互相关联的Activity和一个MainActivity
多个Activity之间跳转简单示意
二、Acitivity生命周期
Activity的声明周期是指Activity所经历的所有状态
Activty的
完整生命周期是指 从第一次调用onCreate（）方法开始，直到调用onDrestroy（）方法位置。
Activity的
可视生命周期是指
自onStart()调用开始直到相应的onStop()调用结束。在此期间，用户可以在屏幕上看到Activity。
Activity的前台生命周期是指 onResume()调用起，至相应的onPause()调用为止。在此期间，Activity位于前台最上面并与用户进行交互。
三、Activity的状态保存
通过onSaveInstance（）方法，回收当前Activty时回调该方法
例：
package com.songjialongs.myapplication;
import android.os.PersistableBundle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;
public class Activity_Lifecycle extends AppCompatActivity {
EditText user_name_et;
CheckBox rem_user_name_cb;
boolean iscckeck = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__lifecycle);
user_name_et = (EditText) findViewById(R.id.user_name_et);
rem_user_name_cb = (CheckBox) findViewById(R.id.rem_user_name_cb);
iscckeck = savedInstanceState.getBoolean("remname");
rem_user_name_cb.setChecked(iscckeck);
final String name = savedInstanceState.getString("name");
rem_user_name_cb.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
if (b) {
user_name_et.setText(name);
iscckeck = true;
} else {
iscckeck = false;
}
}
});
}
@Override
public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
super.onSaveInstanceState(outState, outPersistentState);
String content = user_name_et.getText().toString();
outState.putString("name", content);//参数为String Key，String Value
outState.putBoolean("remname", iscckeck);//参数为String Key，boolean Value
}
}
layout代码：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/user_name_txt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:layout_marginTop="20dp"
android:text="用户名:"
android:textSize="32sp" />
<EditText
android:id="@+id/user_name_et"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginRight="20dp"
android:layout_marginTop="20dp"
android:layout_toRightOf="@id/user_name_txt" />
<CheckBox
android:id="@+id/rem_user_name_cb"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@id/user_name_et"
android:layout_below="@id/user_name_et"
android:text="记住密码"
android:textSize="24sp" />
</RelativeLayout>
四、Activity启动模式LaunchMode
LaunchMode是在Activity跳转的过程中，决定是否生成新的Activity，是否重用已经存在的，是否和其他实例公用一个task stack
1、Standard模式
Standard模式是默认启动模式，每次跳转Activity即StartActivty时都会生成一个新的Activity并压入系统默认的task stack中
package com.songjialongs.myapplication.LuancherMode;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class MainActivity extends AppCompatActivity {
TextView activty_A_Txt;
Button activty_A_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__main);
activty_A_Txt = (TextView) findViewById(R.id.activty_a_txt);
activty_A_Btn = (Button) findViewById(R.id.activity_a_btn);
activty_A_Txt.setText(this.toString());
activty_A_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, Activity_Stardard_B.class);
startActivity(intent);
}
});
}
}
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class Activity_Stardard_B extends AppCompatActivity {
TextView activty_B_Txt;
Button activty_B_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__stardard);
activty_B_Txt = (TextView) findViewById(R.id.stardard_b_txt);
activty_B_Btn = (Button) findViewById(R.id.stardard_b_btn);
activty_B_Txt.setText(this.toString());
activty_B_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Activity_Stardard_B.this, MainActivity.class);
startActivity(intent);
}
});
}
}
2、SingleTop模式
要跳转的Activity已经
存在与系统的task中，并且位于
栈顶，就使用栈顶的相同的Activity；若不存在，则创建一个新的Activty，并压入系统默认的task stack
package com.songjialongs.myapplication.LuancherMode;
import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class MainActivity extends AppCompatActivity {
TextView activty_A_Txt;
Button activty_A_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__main);
activty_A_Txt = (TextView) findViewById(R.id.activty_a_txt);
activty_A_Btn = (Button) findViewById(R.id.activity_a_btn);
activty_A_Txt.setText(this.toString());
activty_A_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, Activity_SingleTop_B.class);
startActivity(intent);
}
});
}
}
package com.songjialongs.myapplication.LuancherMode;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class Activity_SingleTop_B extends AppCompatActivity {
TextView singletop_B_Btn_Txt;
Button singletop_B_Btn_btn;
Button singletop_BtoA_Btn_Txt;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__singletop__b);
singletop_B_Btn_Txt = (TextView) findViewById(R.id.singletop_b_btn_txt);
singletop_B_Btn_btn = (Button) findViewById(R.id.singletop_b_btn);
singletop_BtoA_Btn_Txt = (Button) findViewById(R.id.singletop_btoa_btn);
singletop_B_Btn_Txt.setText(this.toString());
singletop_B_Btn_btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Activity_SingleTop_B.this, Activity_SingleTop_B.class);
startActivity(intent);
}
});
singletop_BtoA_Btn_Txt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Activity_SingleTop_B.this, MainActivity.class);
startActivity(intent);
}
});
}
}
3、SingleTask模式
要跳转的Activity已经存在与栈中，就直接跳转至这个Activity；若不存在就创建一个新的Activity，并压入系统默认的task stack
package com.songjialongs.myapplication.LuancherMode;
import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class MainActivity extends AppCompatActivity {
TextView activty_A_Txt;
Button activty_A_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__main);
activty_A_Txt = (TextView) findViewById(R.id.activty_a_txt);
activty_A_Btn = (Button) findViewById(R.id.activity_a_btn);
activty_A_Txt.setText(this.toString());
activty_A_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, Activity_SingleTask_B.class);
startActivity(intent);
}
});
}
}
package com.songjialongs.myapplication.LuancherMode;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class Activity_SingleTask_B extends AppCompatActivity {
TextView activty_B_Txt;
Button activty_B_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__singletask);
activty_B_Txt = (TextView) findViewById(R.id.singletask_b_txt);
activty_B_Btn = (Button) findViewById(R.id.singletask_b_btn);
activty_B_Txt.setText(this.toString());
activty_B_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Activity_SingleTask_B.this, MainActivity.class);
startActivity(intent);
}
});
}
}
4、SingleInstance模式
跳转Acitivity 新建一个task stack，将跳转的Activity压入这个task stack，并且新建的task stack只有一个Activity
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class MainActivity extends AppCompatActivity {
TextView activty_A_Txt;
Button activty_A_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
activty_A_Txt = (TextView) findViewById(R.id.activty_a_txt);
activty_A_Btn = (Button) findViewById(R.id.activity_a_btn);
activty_A_Txt.setText(this.toString() + "：栈：" + getTaskId());
activty_A_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(MainActivity.this, Activity_SingleInstance_B.class);
startActivity(intent);
}
});
}
}
package com.songjialongs.myapplication.LuancherMode;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.songjialongs.myapplication.R;
public class Activity_SingleInstance_B extends AppCompatActivity {
TextView singinstance_B_Txt;
Button singinstance_B_Btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity__singleinstance);
singinstance_B_Txt = (TextView) findViewById(R.id.singleinstance_b_txt);
singinstance_B_Btn = (Button) findViewById(R.id.singleinstance_b_btn);
singinstance_B_Txt.setText(this.toString() + "：栈：" + getTaskId());
singinstance_B_Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(Activity_SingleInstance_B.this, Activity_SingleInstance_B.class);
startActivity(intent);
}
});
}
}