Android - Runtime Changes (2) - Handling the Configuration

相較於 onRetainNonConfigurationInstance() 和 getLastNonConfigurationInstance()來控制Activity資料的保存，另一個選擇方式是改寫 AndroidManifest.xml裡面Activity的Configuration屬性。正常情況下，執行Activity然後旋轉方向後的 Life Cycle如下:
onCreate()
onStart()
onResume()

onPause()
onStop()
onDestroy()
onCreate()
onStart()
onResume()

然後我們改變Configuration後如下:
        <activity android:name=".Main"
                  android:configChanges="orientation|keyboardHidden"
                  android:label="@string/app_name">

如此一來，執行程式後，再把畫面旋轉或是開啟硬體鍵盤後的Life Cycle如下:

onCreate()
onStart()
onResume()

也就是不會消滅後再重新啟動。如果想要在旋轉畫面後做一些特別的事情，可以@Override
onConfigurationChanged() 如下:

public class Main extends Activity {
    /** Called when the activity is first created. */
    private final static String TAG = "TestLife";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.d(TAG, "onCreate()");
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
   
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);

        // Checks the orientation of the screen
        if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
            Log.d(TAG, "landscape");         
        } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
            Log.d(TAG, "portrait");  
            Toast.makeText(this, "portrait", Toast.LENGTH_SHORT).show();
        }
        // Checks whether a hardware keyboard is available
        if (newConfig.hardKeyboardHidden == Configuration.HARDKEYBOARDHIDDEN_NO) {
            Log.d(TAG, "keyboard visible"); 
        } else if (newConfig.hardKeyboardHidden == Configuration.HARDKEYBOARDHIDDEN_YES) {
            Log.d(TAG, "keyboard hidden");    
        }
    }  
    
    @Override
    public void onStart() {
        super.onStart();
        Log.d(TAG, "onStart()");
    }
   
    @Override
    public void onRestart() {
        super.onRestart();
        Log.d(TAG, "onRestart()");
    }
   
    @Override
    public void onResume() {
        super.onResume();
        Log.d(TAG, "onResume()");
    }
   
    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG, "onPause()");
    }
   
    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG, "onStop()");
    }
   
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy()");
    }
}

其它需要注意的事項請參考官網說明，另外Configuration的其他選項還有這些可以使用。