Android 广播机制

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Android

Android BroadcastReceiver Broadcast Parcel Bundle传递对象

一听广播二字，我们第一感觉就会联想到了小时候村里的广播播音，收音机等。对于广播来说，广播发送方 并不在意广播接收方 动作，接收到广播时如何处理，需要干什么，那是你接受者事。其实，Android 中的广播又何尝不是呢。

Android 中有各式各样的广播，各种广播在Android 系统中运行，当系统/应用程序运行时便会向 Android 注册各种广播，Android 接收到广播会便会判断哪种广播需要哪种事件，然后向不同需要事件的应用程序注册事件，不同的广播可能处理不同的事件也可能处理相同的广播事件，这时就需要 Android 系统为我们做筛选。

无论怎么，既然是广播机制，最最起码的必须要有广播方式者，Android中，广播发送有三种形式，即，sendBroadcast(),sendOrderedBroadcast(),sendStickyBroadcast()，至于这三种的区别google一下遍地都是。此外就是接收端，只有接收了才能做相应的动作，如果没有接收，那么广播就没有什么意义了。而Android广播接收使用了2种方式，它们的是继承了BroadcastReceiver，实现其方法onReceive，在广播被接收之后，接收者就可以在onReceive中做各种各样的处理。

下面是广播机制中的2中接收方式的测试Demo；

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<TextView android:layout_width="fill_parent"
		android:layout_height="wrap_content" android:text="@string/hello" />
	<LinearLayout android:orientation="horizontal"
		android:layout_width="fill_parent" android:layout_height="wrap_content">
		<Button android:layout_height="wrap_content" android:text="@string/static_label"
			android:layout_width="wrap_content" android:id="@+id/button1" />
		<Button android:text="@string/dynamic_code" android:id="@+id/button2"
			android:layout_width="wrap_content" android:layout_height="wrap_content" />
	</LinearLayout>
	<TextView android:text="TextView" android:id="@+id/textView1"
		android:layout_width="fill_parent" android:layout_height="wrap_content" />
</LinearLayout>

MainActivity实现了主要广播接收发送的简短方式：

public class MyTestBroadcarsReceiverActivity extends Activity {
	public static final String CODELOGIN_INTENTFILTER_ACTION = "com.testbroadcastreceiver.TestBroadcastReceiver.CodeLogin";
	public static final String LABELLOGIN_INTENTFILTER_ACTION = "com.testbroadcastreceiver.TestBroadcastReceiver.LabelLogin";

	public static Context mBase;

	private Button codeLoginBtn;
	private Button labelLoginBtn;
	public TextView broadcastReceiverTV;

	private TextViewParcel mTextViewParcel;

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		mBase = this;

		initComponent();

		mTextViewParcel = new TextViewParcel(broadcastReceiverTV);
		mCodeLogin_BroadcastReceiver = new CodeLogin_BroadcastReceiver();
	}

	@Override
	protected void onStart() {
		super.onStart();

		mFilter = new IntentFilter();
		mFilter.addAction(CODELOGIN_INTENTFILTER_ACTION);
		if (mCodeLogin_BroadcastReceiver != null && mFilter != null) {
			mBase.registerReceiver(mCodeLogin_BroadcastReceiver, mFilter);
		}
	}

	@Override
	protected void onStop() {
		super.onStop();

		if (mCodeLogin_BroadcastReceiver != null) {
			mBase.unregisterReceiver(mCodeLogin_BroadcastReceiver);
		}
	}

	private void initComponent() {
		labelLoginBtn = (Button) findViewById(R.id.button1);
		if (labelLoginBtn != null) {
			labelLoginBtn.setOnClickListener(LabelLogin_SendBroadcastListener);
		}

		codeLoginBtn = (Button) findViewById(R.id.button2);
		if (codeLoginBtn != null) {
			codeLoginBtn.setOnClickListener(CodeLogin_SendBroadcastListener);
		}

		broadcastReceiverTV = (TextView) findViewById(R.id.textView1);
		if (broadcastReceiverTV != null) {
			broadcastReceiverTV.setText("Test BroadcastReceiver");
		}
	}

	public OnClickListener LabelLogin_SendBroadcastListener = new OnClickListener() {

		@Override
		public void onClick(View v) {
			Log.d("TestBroadcastReceiver", "onClick()");
			labelLogin_sendBroadcart();
		}
	};

	public OnClickListener CodeLogin_SendBroadcastListener = new OnClickListener() {

		@Override
		public void onClick(View v) {
			codeLogin_sendBroadcart();
		}
	};

	private void codeLogin_sendBroadcart() {
		Intent intent = new Intent();
		intent.setAction(CODELOGIN_INTENTFILTER_ACTION);

		Bundle extras = new Bundle();
		String str = mBase.getString(R.string.dynamic_code) + ":\n    "
				+ mBase.getString(R.string.dynamic_code_content) + "\n    ";

		String s = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
		char c[] = s.toCharArray();
		for (int i = 0; i < 100; i++) {
			int randomId = new Random().nextInt(s.length());
			str += c[randomId];
		}

		extras.putString("TVText_codeLogin", str);
		intent.putExtras(extras);
		mBase.sendBroadcast(intent);
	}

	private void labelLogin_sendBroadcart() {
		Intent intent = new Intent();
		intent.setAction(LABELLOGIN_INTENTFILTER_ACTION);

		Bundle extras = new Bundle();
		String str = mBase.getString(R.string.static_label) + ":\n    "
				+ mBase.getString(R.string.static_label_content) + "\n    ";

		String s = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
		char c[] = s.toCharArray();
		for (int i = 0; i < 100; i++) {
			int randomId = new Random().nextInt(s.length());
			str += c[randomId];
		}

		extras.putString("TVText_labelLogin", str);
		extras.putParcelable("TVWidget_labelLogin", mTextViewParcel);
		intent.putExtras(extras);
		mBase.sendBroadcast(intent);
	}

	private CodeLogin_BroadcastReceiver mCodeLogin_BroadcastReceiver;
	private IntentFilter mFilter;

	public class CodeLogin_BroadcastReceiver extends BroadcastReceiver {

		public CodeLogin_BroadcastReceiver() {
			Log.d("CodeLogin_BroadcastReceiver",
					"new CodeLogin_BroadcastReceiver()");
		}

		@Override
		public void onReceive(Context context, Intent intent) {
			Log.d("CodeLogin_BroadcastReceiver", "onReceive()");

			Bundle extras = intent.getExtras();
			if (extras != null && broadcastReceiverTV != null) {
				String str = extras.getString("TVText_codeLogin");
				broadcastReceiverTV.setText(str);
			}
		}
	}

}

对于静态注册方式，这里实现了利用Bundle传递对象的方式：

package com.testbroadcastreceiver.br;
public class LabelLogin_BroadcastReceiver extends BroadcastReceiver {

	private TextViewParcel mTextViewParcel;

	public LabelLogin_BroadcastReceiver() {
		Log.d("LabelLogin_BroadcastReceiver", "new LabelLogin_BroadcastReceiver()");
	}

	@Override
	public void onReceive(Context context, Intent intent) {
		Log.d("LabelLogin_BroadcastReceiver", "onReceive()");

		Bundle extras = intent.getExtras();
		if (extras != null) {
			if (intent.hasExtra("TVWidget_labelLogin")) {
				extras.getParcelable("TVWidget_labelLogin");
				mTextViewParcel = extras.getParcelable("TVWidget_labelLogin");
			}
			String str = extras.getString("TVText_labelLogin");
			if (mTextViewParcel != null
					&& mTextViewParcel.getBroadcastReceiverTV() != null)
				mTextViewParcel.getBroadcastReceiverTV().setText(str);
		}
	}
}

Bundle传递对象的处理方式，注意TextViewParcel中writeValue()和readValue()的写法：

public class BroadcastReceiverTV extends Binder {
	
	public TextView mTextView;

}

package com.testbroadcastreceiver.textviewparcel;
public class TextViewParcel implements Parcelable {

	private BroadcastReceiverTV broadcastReceiverTV = new BroadcastReceiverTV();

	public TextViewParcel(TextView mTextView) {
		broadcastReceiverTV.mTextView = mTextView;
	}

	public TextViewParcel(Parcel in) {
		broadcastReceiverTV = (BroadcastReceiverTV)in.readValue(BroadcastReceiverTV.class
				.getClassLoader());
	}

	public TextView getBroadcastReceiverTV() {
		return broadcastReceiverTV.mTextView;
	}

	public void setBroadcastReceiverTV(TextView broadcastReceiverTV) {
		this.broadcastReceiverTV.mTextView = broadcastReceiverTV;
	}

	@Override
	public int describeContents() {
		return 0;
	}

	@Override
	public void writeToParcel(Parcel dest, int flags) {
		dest.writeValue(broadcastReceiverTV);
	}

	public static final Parcelable.Creator<TextViewParcel> CREATOR = new Creator<TextViewParcel>() {

		@Override
		public TextViewParcel[] newArray(int size) {
			return new TextViewParcel[size];
		}

		@Override
		public TextViewParcel createFromParcel(Parcel source) {
			return new TextViewParcel(source);
		}
	};

}