Android第一行代码阅读笔记-2
七、运行时权限
低于6.0系统只需要在AndroidManifest.xml加入需要的权限，用户同意安装时会统一授予。6.0之后加入运行时权限，即在使用过程中授予权限，可以随时回收权限。
普通权限：申请时系统自动进行授权。
危险权限：设计隐私和设备安全需要手动授权。9组24个。
权限列表：http://developer.android.google.cn/reference/android/Manifest.permission.html
| 权限组 | 权限 |
|---|---|
CALENDAR |
|
CAMERA |
|
CONTACTS |
|
LOCATION |
|
MICROPHONE |
|
PHONE |
|
SENSORS |
|
SMS |
|
STORAGE |
|
1、在AndroidManifest.xml中声明
......
2、在代码中申请
处理授予和不授予的执行代码
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
......
makeCall.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(ContextCompat.checkSelfPermission(ManiActivity.this, Manifest.permission.CALL_PHONE)
!= PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(ManiActivity.this, new String[] {Manifest.permission.CALL_PHONE}, 1)
}
});
}
private void call() {
try {
Intent intent = new Intent(Intent.ACTION_CALL);
intent.setData(Uri.parse("tel:10086"));
startActivity(intent);
} catch (SecurityException e) {
e.printStackTrace();
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case 1:
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
call();
} else {
Toast.makeText(this, "You denied the permission", Toast.LENGTH_SHORT).show();
}
break;
default:
}
}
} 八、ContentProvider
APP通过ContentProvider对其数据向外提供访问接口。想要对该数据执行CRUD操作首先要通过Context中的getContentResolver()得到ContentResolver类。通过该类调用insert()等方法。这些方法都要接收一个Uri参数指定内容。
content://author+path
Uri mUri = Uri.parse("content://com.example.app.provider/table1");1、AndroidManifest.xml
.......
2、MyDatabaseHelper
创建数据库
public class MyDatabaseHelper extends SQLiteOpenHelper {
public static final String CREATE_BOOK = "create table Book ("
+ "id integer primary key autoincrement, "
+ "author text, "
+ "price real, "
+ "pages integer, "
+ "name text)";
public static final String CREATE_CATEGORY = "create table Category ("
+ "id integer primary key autoincrement, "
+ "category_name text, "
+ "category_code integer)";
private Context mContext;
public MyDatabaseHelper(Context context, String name,
SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
// Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists Book");
db.execSQL("drop table if exists Category");
onCreate(db);
}
}3、DataBaseProvider.java
创建ContentProvider,需要重写各种操作方法, getType返回Uri对象的MIME类型。
目录：vnd.android.cursor.dir/vnd.com.example.databasetest. provider.category
文件：vnd.android.cursor.item/vnd.com.example.databasetest. provider.category
public class DatabaseProvider extends ContentProvider {
public static final int BOOK_DIR = 0;
public static final int BOOK_ITEM = 1;
public static final int CATEGORY_DIR = 2;
public static final int CATEGORY_ITEM = 3;
public static final String AUTHORITY = "com.example.databasetest.provider";
private static UriMatcher uriMatcher;
private MyDatabaseHelper dbHelper;
static {
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
uriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);/#匹配任意长度数字
uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
}
@Override
public boolean onCreate() {
dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
// 查询数据
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = null;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
cursor = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
cursor = db.query("Book", projection, "id = ?", new String[] { bookId }, null, null, sortOrder);
break;
case CATEGORY_DIR:
cursor = db.query("Category", projection, selection, selectionArgs, null, null, sortOrder);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
cursor = db.query("Category", projection, "id = ?", new String[] { categoryId }, null, null, sortOrder);
break;
default:
break;
}
return cursor;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
// 添加数据
SQLiteDatabase db = dbHelper.getWritableDatabase();
Uri uriReturn = null;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
case BOOK_ITEM:
long newBookId = db.insert("Book", null, values);
uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + newBookId);
break;
case CATEGORY_DIR:
case CATEGORY_ITEM:
long newCategoryId = db.insert("Category", null, values);
uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + newCategoryId);
break;
default:
break;
}
return uriReturn;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
// 更新数据
SQLiteDatabase db = dbHelper.getWritableDatabase();
int updatedRows = 0;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
updatedRows = db.update("Book", values, selection, selectionArgs);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
updatedRows = db.update("Book", values, "id = ?", new String[] { bookId });
break;
case CATEGORY_DIR:
updatedRows = db.update("Category", values, selection, selectionArgs);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
updatedRows = db.update("Category", values, "id = ?", new String[] { categoryId });
break;
default:
break;
}
return updatedRows;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// 删除数据
SQLiteDatabase db = dbHelper.getWritableDatabase();
int deletedRows = 0;
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
deletedRows = db.delete("Book", selection, selectionArgs);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
deletedRows = db.delete("Book", "id = ?", new String[] { bookId });
break;
case CATEGORY_DIR:
deletedRows = db.delete("Category", selection, selectionArgs);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
deletedRows = db.delete("Category", "id = ?", new String[] { categoryId });
break;
default:
break;
}
return deletedRows;
}
@Override
public String getType(Uri uri) {
switch (uriMatcher.match(uri)) {
case BOOK_DIR:
return "vnd.android.cursor.dir/vnd.com.example.databasetest. provider.book";
case BOOK_ITEM:
return "vnd.android.cursor.item/vnd.com.example.databasetest. provider.book";
case CATEGORY_DIR:
return "vnd.android.cursor.dir/vnd.com.example.databasetest. provider.category";
case CATEGORY_ITEM:
return "vnd.android.cursor.item/vnd.com.example.databasetest. provider.category";
}
return null;
}
}4、ManiActivity操作ContentProvider
public class MainActivity extends AppCompatActivity {
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
Button createDatabase = (Button) findViewById(R.id.create_database);
createDatabase.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dbHelper.getWritableDatabase();
}
});
Button addData = (Button) findViewById(R.id.add_data);
addData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
// 开始组装第一条数据
values.put("name", "The Da Vinci Code");
values.put("author", "Dan Brown");
values.put("pages", 454);
values.put("price", 16.96);
db.insert("Book", null, values); // 插入第一条数据
values.clear();
// 开始组装第二条数据
values.put("name", "The Lost Symbol");
values.put("author", "Dan Brown");
values.put("pages", 510);
values.put("price", 19.95);
db.insert("Book", null, values); // 插入第二条数据
}
});
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("price", 10.99);
db.update("Book", values, "name = ?", new String[] { "The Da Vinci Code" });
}
});
Button deleteButton = (Button) findViewById(R.id.delete_data);
deleteButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete("Book", "pages > ?", new String[] { "500" });
}
});
Button queryButton = (Button) findViewById(R.id.query_data);
queryButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
// 查询Book表中所有的数据
Cursor cursor = db.query("Book", null, null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
String name = cursor.getString(cursor.getColumnIndex("name"));
String author = cursor.getString(cursor.getColumnIndex("author"));
int pages = cursor.getInt(cursor.getColumnIndex("pages"));
double price = cursor.getDouble(cursor.getColumnIndex("price"));
} while (cursor.moveToNext());
}
cursor.close();
}
});
}
}九、Service
Service实现APP后台运行，适合不与用户交互但需长期运行的任务。服务不运行在单独的进程，依赖于创建服务时所在应用程序进程。服务默认不开启线程，即它默认运行在主线程需要手动在内部创建线程。
1、多线程操作
#继承方式
class MyThread extend Thread {
public void run() {
}
}
//启动
new MyThread().start();
#接口方式
class MyThread implements Runnable {
public void run() {
}
}
//启动
MyThread mThread = new MyThread();
new Thread(mThread).start();
#匿名类
new Thread(new Runnable() {
public void run() {
}
}).start();2、UI操作
Android中的异步消息主要由4部分组成：Message, Handler, MessageQueue和Looper。MessageQueue用于存放通过Handler发送的消息，这部分消息已知存在于消息队列等待被处理。每个线程只有一个MessageQueue对象。Looper是每个线程MessageQueue的管家，调用Looper的loop()方法后，就会将它取出并传递到Handler的handlerMessage()方法中。每个线程也只有一个Looper对象。
一般首先在主线程中创建一个Handler对象，并重写HandlerMessage()方法。当子线程需要进程UI操作时，创建一个Message对象并通过Handler发出这条消息。之后这条消息会被添加到MessageQueue中等待被处理。而Looper则一直尝试从MessageQueue中取出待处理消息，分发到handler中的handleMessage()方法中。
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
public static final int UPDATE_TEXT = 1;
private TextView text;
private Handler handler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case UPDATE_TEXT:
// 在这里可以进行UI操作
text.setText("Nice to meet you");
break;
default:
break;
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text = (TextView) findViewById(R.id.text);
Button changeText = (Button) findViewById(R.id.change_text);
changeText.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.change_text:
new Thread(new Runnable() {
@Override
public void run() {
Message message = new Message();
message.what = UPDATE_TEXT;
handler.sendMessage(message); // 将Message对象发送出去
}
}).start();
break;
default:
break;
}
}
}3、Service基本用法
onCreate()方法是在服务第一次创建时候调用，而onStartCommand()方法则是每次启动服务都会调用。onBind()方法在Activity绑定服务时回调。
MainService.java
public class MyService extends Service {
public MyService() {
}
private DownloadBinder mBinder = new DownloadBinder();
class DownloadBinder extends Binder {
public void startDownload() {
Log.d("MyService", "startDownload executed");
}
public int getProgress() {
Log.d("MyService", "getProgress executed");
return 0;
}
}
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public void onCreate() {
super.onCreate();
Log.d("MyService", "onCreate executed");
Intent intent = new Intent(this, MainActivity.class);
PendingIntent pi = PendingIntent.getActivity(this, 0, intent, 0);
Notification notification = new NotificationCompat.Builder(this)
.setContentTitle("This is content title")
.setContentText("This is content text")
.setWhen(System.currentTimeMillis())
.setSmallIcon(R.mipmap.ic_launcher)
.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher))
.setContentIntent(pi)
.build();
startForeground(1, notification);//启动前台服务
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.d("MyService", "onStartCommand executed");
return super.onStartCommand(intent, flags, startId);
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d("MyService", "onDestroy executed");
}
}MainActivity
重写ServiceConnection的onServiceConnection()和onServiceDisconnected(),他们在活动和服务绑定和解绑时调用。每调用一个startService（）,onStartCommand()就会执行一次，但实际上每个服务只存在一个实例。所以不管调用了多少次startService(), 只需要调用一次stopService()或stopSelf()。调用bindService()来获得一个和服务的持久连接。这时会回调onBind()方法。如果该服务还未创建则先调用onCreate()。
如果对一个服务既调用了startService()又调用了bindService()，则必须同时调用stopService()和unbindService()方法，onDestroy()方法才会执行。
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
private MyService.DownloadBinder downloadBinder;
private ServiceConnection connection = new ServiceConnection() {
@Override
public void onServiceDisconnected(ComponentName name) {
}
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
downloadBinder = (MyService.DownloadBinder) service;
downloadBinder.startDownload();
downloadBinder.getProgress();
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button startService = (Button) findViewById(R.id.start_service);
Button stopService = (Button) findViewById(R.id.stop_service);
startService.setOnClickListener(this);
stopService.setOnClickListener(this);
Button bindService = (Button) findViewById(R.id.bind_service);
Button unbindService = (Button) findViewById(R.id.unbind_service);
bindService.setOnClickListener(this);
unbindService.setOnClickListener(this);
Button startIntentService = (Button) findViewById(R.id.start_intent_service);
startIntentService.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.start_service:
Intent startIntent = new Intent(this, MyService.class);
startService(startIntent); // 启动服务
break;
case R.id.stop_service:
Intent stopIntent = new Intent(this, MyService.class);
stopService(stopIntent); // 停止服务
break;
case R.id.bind_service:
Intent bindIntent = new Intent(this, MyService.class);
bindService(bindIntent, connection, BIND_AUTO_CREATE); // 绑定服务
break;
case R.id.unbind_service:
unbindService(connection); // 解绑服务
break;
case R.id.start_intent_service:
// 打印主线程的id
Log.d("MainActivity", "Thread id is " + Thread.currentThread(). getId());
Intent intentService = new Intent(this, MyIntentService.class);
startService(intentService);
break;
default:
break;
}
}
}IntentService
服务默认执行在主线程中，如果需要处理耗时操作需要在Service中手动开启和关闭子线程。Android设计了IntentService类，启动后自动执行其中的onHandleIntent()方法，执行完执行onDestroy()方法。
public class MyIntentService extends IntentService {
public MyIntentService() {
super("MyIntentService"); // 调用父类的有参构造函数
}
@Override
protected void onHandleIntent(Intent intent) {
// 打印当前线程的id
Log.d("MyIntentService", "Thread id is " + Thread.currentThread(). getId());
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d("MyIntentService", "onDestroy executed");
}
}10、Application
Android提供一个Application类，每当程序启动时，系统自动初始化这个类。我们可以自己定制这个类，以便获取全局信息，如Context。 程序运行时自动执行onCreate()， 在Activity中只需要执行 MyApplication.getContext（）
public class MyApplication extends Application {
private static Context context;
@override
public void onCreate() {
context = getApplicationCcontext();
}
public static Context getContext() {
return context;
}
} 还需要在AndroidManifest.xml中声明这个Application