如何在Android中获取当前的前台活动上下文？
本示例演示了如何在Android中获取当前的前台活动上下文
步骤1-在AndroidStudio中创建一个新项目，转到File⇒NewProject并填写所有必需的详细信息以创建一个新项目。
第2步-将以下代码添加到src/MyApp.java
package app.nhooo.com.sample ;
import android.app.Activity ;
import android.app.Application ;
public class MyApp extends Application {
private Activity mCurrentActivity = null;
@Override
public void onCreate () {
super .onCreate() ;
}
public Activity getCurrentActivity () {
return mCurrentActivity ;
}
public void setCurrentActivity (Activity mCurrentActivity) {
this . mCurrentActivity = mCurrentActivity ;
}
}步骤3-将以下代码添加到src/MyBaseActivity.java
package app.nhooo.com.sample ;
import android.app.Activity ;
import android.os.Bundle ;
import android.support.v7.app.AppCompatActivity ;
public class MyBaseActivity extends AppCompatActivity {
protected MyApp mMyApp ;
public void onCreate (Bundle savedInstanceState) {
super .onCreate(savedInstanceState) ;
mMyApp = (MyApp) this .getApplicationContext() ;
}
protected void onResume () {
super .onResume() ;
mMyApp .setCurrentActivity( this ) ;
}
protected void onPause () {
clearReferences() ;
super .onPause() ;
}
protected void onDestroy () {
clearReferences() ;
super .onDestroy() ;
}
private void clearReferences () {
Activity currActivity = mMyApp .getCurrentActivity() ;
if ( this .equals(currActivity))
mMyApp .setCurrentActivity( null ) ;
}
}步骤4-将以下代码添加到src/MainActivity.java
package app.nhooo.com.sample ;
import android.app.Activity ;
import android.support.v7.app.AppCompatActivity ;
import android.os.Bundle ;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate (Bundle savedInstanceState) {
super .onCreate(savedInstanceState) ;
setContentView(R.layout. activity_main ) ;
Activity currentActivity = ((MyApp)
getApplicationContext()).getCurrentActivity() ;
}
}第5步-将以下代码添加到androidManifest.xml
<? xml version= "1.0" encoding= "utf-8" ?>
<manifest xmlns: android = "http://schemas.android.com/apk/res/android"
package= "app.nhooo.com.sample" >
<uses-permission android :name= "android.permission.CALL_PHONE" />
<application
android :name= ".MyApp"
android :allowBackup= "true"
android :icon= "@mipmap/ic_launcher"
android :label= "@string/app_name"
android :roundIcon= "@mipmap/ic_launcher_round"
android :supportsRtl= "true"
android :theme= "@style/AppTheme" >
<activity android :name= ".MainActivity" >
<intent-filter>
<action android :name= "android.intent.action.MAIN" />
<category android :name= "android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android :name= ".MyBaseActivity" />
</application>
</manifest>