BroadcastReceiver小记

一、 广播发送及广播类型

1. Normal Broadcast：普通广播（同步广播）

Intent broadcast = new Intent();
broadcast.setAction("com.example.crackme"); 
broadcast.putExtra("test", "发送广播");
sendBroadcast(broadcast);

2. System Broadcast：系统广播
3. Ordered Broadcast：有序广播
4. Local Broadcast：app应用内广播

二、广播接收器注册

1. 静态注册

<receiver android:name=".WellcomeActivity$MyBroadcastReciver">
    <intent-filter>
          <action android:name="com.example.crackme"/>
     </intent-filter>
</receiver>

2. 动态注册

myBroadcastReciver = new MyBroadcastReciver();
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("com.example.crackme");
registerReceiver(myBroadcastReciver, intentFilter);

三、BroadcastReceiver接收广播

public class MyBroadcastReciver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            Log.v("消息", "来自GoodByeActivity的广播");
            String str = intent.getExtras().getString("test");
            Toast.makeText(context, str, Toast.LENGTH_SHORT).show();
            Toast.makeText(context, "来自GoodByeActivity的广播",Toast.LENGTH_SHORT).show();
            finish();
        }
}

这样一个完整的发送广播和接收广播的过程就完成了。

这次做的功能是：在一个Activity中销毁另外一个Activity。
方法一：利用广播接收者
第一个Activity

public class MainActivity extends AppCompatActivity {
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button) findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, WellcomeActivity.class);
                startActivity(intent);
                finish();
            }
        });
    }
}

第二个Activity：

public class WellcomeActivity extends AppCompatActivity {
    private TextView textView;
    MyBroadcastReciver myBroadcastReciver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wellcome);
        textView = (TextView) findViewById(R.id.textView);
        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(WellcomeActivity.this, GoodByeActivity.class);
                startActivity(intent);
                myBroadcastReciver = new MyBroadcastReciver();
                IntentFilter intentFilter = new IntentFilter();            
                intentFilter.addAction("com.example.crackme");
                registerReceiver(myBroadcastReciver, intentFilter);

            }
        });
    }
    public class MyBroadcastReciver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            Log.v("消息", "来自GoodByeActivity的广播");
            String str = intent.getExtras().getString("test");
            Toast.makeText(context, str, Toast.LENGTH_SHORT).show();
            Toast.makeText(context, "来自GoodByeActivity的广播",Toast.LENGTH_SHORT).show();
            finish();
        }
    }
    @Override
    protected void onDestroy() {
        if (myBroadcastReciver != null){
            unregisterReceiver(myBroadcastReciver);
        }
        super.onDestroy();

    }
}

第三个Activity:

public class GoodByeActivity extends AppCompatActivity {
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_good_bye);
        button = (Button) findViewById(R.id.button2);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent broadcast = new Intent();          
                broadcast.setAction("com.example.crackme");
                broadcast.putExtra("test", "发送广播);
                sendBroadcast(broadcast);
                Intent intent = new Intent(GoodByeActivity.this, MainActivity.class);
                startActivity(intent);
                finish();
            }
        });
    }
}

注意：这里实例化了两个Intent对象，他们的作用不同。第一个Intent用于发送广播，第二个Intent实现页面跳转。这里不能将它们写在一起，写在一起在第二个Activity就无法收到广播，如下写法：

                Intent broadcast = new Intent(GoodByeActivity.this, MainActivity.class);          
                broadcast.setAction("com.example.crackme");
                broadcast.putExtra("test", "发送广播);
                sendBroadcast(broadcast);               
                startActivity(broadcast);

第二种方法：利用startActivityForResult()同样可以实现
第一个Activity不变
第二个Activity修改为：

public class WellcomeActivity extends AppCompatActivity {
    private TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wellcome);
        textView = (TextView) findViewById(R.id.textView);
        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(WellcomeActivity.this, GoodByeActivity.class);
                startActivityForResult(intent, 1);
            }
        });
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (resultCode){
            case 1:
                Log.v("消息", "来自GoodByeActivity的结果码");
                finish();
        }
        super.onActivityResult(requestCode, resultCode, data);
    } 
}

第三个Activity修改为：

public class GoodByeActivity extends AppCompatActivity {
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_good_bye);
        button = (Button) findViewById(R.id.button2);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent();
                setResult(1, intent);
                finish();
            }
        });
    }
}

就这个功能而言似乎第二种方法更简洁