1. Application的使用
多个组件之间数据共享
举例:两个Activity之间数据共享
Application 对同一个应用程序是唯一的,所以可以使用Application进行数据共享
定义两个Activity: MainActivity.java 和 MainActivity2.java, 代码是一样的
TextView tv;
EditText et;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main_activity2);
setContentView(R.layout.activity_main2);
tv = (TextView) findViewById(R.id.tv);
et = (EditText) findViewById(R.id.et);
tv.setText("共享数据:" + getApp().getTextData());
findViewById(R.id.btnTextData).setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
getApp().setTextData(et.getText().toString());
tv.setText("共享数据:" + et.getText().toString());
}
});
}
public App getApp() {
return ((App)getApplicationContext());
}
定义一个类App,集成Application
public class App extends Application {
private String textData = "default";
public void setTextData(String textData) {
this.textData = textData;
}
public String getTextData() {
return textData;
}
}
修改AndroidManifest.xml文件, 使用自定义的Application,两个Activity都是入口:
<application
android:name="com.carloz.learnapplication.App"
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.carloz.learnapplication.MainActivity2"
android:label="@string/title_activity_main_activity2" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
结果,在一个Activity修改App的数据,在另一个Activity都能获取到
2. Application的生命周期
给应用程序配置,自定义的Application,然后在Application的生命周期中做一些操作
public class App extends Application {
@Override
public void onCreate() {
// 程序创建的时候执行
Log.d(TAG, "onCreate");
super.onCreate();
}
@Override
public void onTerminate() {
// 程序终止的时候执行
Log.d(TAG, "onTerminate");
super.onTerminate();
}
@Override
public void onLowMemory() {
// 低内存的时候执行
Log.d(TAG, "onLowMemory");
super.onLowMemory();
}
@Override
public void onTrimMemory(int level) {
// 程序在内存清理的时候执行
Log.d(TAG, "onTrimMemory");
super.onTrimMemory(level);
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
Log.d(TAG, "onConfigurationChanged");
super.onConfigurationChanged(newConfig);
}
}
打开Activity
08-16 15:16:27.142: D/CARLOZ - Application(28202): onCreate
08-16 15:16:27.172: D/CARLOZ - MainActivity3(28202): onCreate
08-16 15:16:27.232: D/CARLOZ - MainActivity3(28202): onStart
08-16 15:16:27.232: D/CARLOZ - MainActivity3(28202): onResume
HOME键退出应用程序
08-16 15:16:55.372: D/CARLOZ - MainActivity3(28202): onPause
08-16 15:16:55.942: D/CARLOZ - MainActivity3(28202): onStop
08-16 15:16:55.952: D/CARLOZ - Application(28202): onTrimMemory 回收内存
重新打开应用程序
08-16 15:17:20.962: D/CARLOZ - MainActivity3(28202): onRestart
08-16 15:17:20.962: D/CARLOZ - MainActivity3(28202): onStart
08-16 15:17:20.962: D/CARLOZ - MainActivity3(28202): onResume
长按MENU键,打开Recent TASK
08-16 15:17:28.972: D/CARLOZ - MainActivity3(28202): onPause
08-16 15:17:28.992: D/CARLOZ - MainActivity3(28202): onStop
08-16 15:17:29.022: D/CARLOZ - Application(28202): onTrimMemory
彻底关闭应用程序
08-16 15:17:31.542: D/CARLOZ - MainActivity3(28202): onDestroy