Activity中recreate方法的应用

Posted 2020-10-23 llguanli

參考两篇文章：http://blog.csdn.net/watermusicyes/article/details/47392949

? ??http://blog.csdn.net/droyon/article/details/21275797

recreate能够使用在日间/夜间模式的切换，那么调用recreate()函数将会运行哪些方法呢？

代码：

public class MainActivity extends FragmentActivity implements OnClickListener {
	private Button btn;
	private int mTheme;
	private String THEME = "theme";
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		if (savedInstanceState != null) {
			mTheme = savedInstanceState.getInt(THEME);
			switchTheme(mTheme);
		}
		
		setContentView(R.layout.activity_main);
		btn = (Button) findViewById(R.id.btn);
		btn.setOnClickListener(this);

		Log.e(MainActivity.class.getName(), "onCreate");
	}
	
	@Override  
    protected void onSaveInstanceState(Bundle savedInstanceState) {  
        super.onSaveInstanceState(savedInstanceState);  
        Log.e(MainActivity.class.getName(), "onSaveInstanceState");
        savedInstanceState.putInt(THEME, mTheme);
    } 
	
	@Override
	protected void onRestoreInstanceState(Bundle savedInstanceState) {
		super.onRestoreInstanceState(savedInstanceState);
		Log.e(MainActivity.class.getName(), "onRestoreInstanceState");
	}
	
	@Override
	protected void onStart() {
		super.onStart();
		Log.e(MainActivity.class.getName(), "onStart");

	}

	@Override
	protected void onResume() {
		super.onResume();
		Log.e(MainActivity.class.getName(), "onResume");

	}
	
	private void switchTheme(int theme) {
		switch (mTheme) {
		case android.R.style.Theme_Holo_Light:
			mTheme = android.R.style.Theme_Black_NoTitleBar;
			break;
		case android.R.style.Theme_Black_NoTitleBar:
			mTheme = android.R.style.Theme_Holo_Light;
			break;
		default:
			mTheme = android.R.style.Theme_Holo_Light;
			break;
		}
		setTheme(mTheme);
	}

	@SuppressLint("NewApi")
	@Override
	public void onClick(View v) {
		recreate();
	}
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.testandroid.MainActivity" >

    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="recreate" />

</RelativeLayout>

点击recreatebutton能够看到打印相关的信息：

能够看到这里调用recreate方法会比正常启动Activity多调用了onSaveInstanceState和onRestoreInstanceState。而且onSaveInstanceState在onCreate方法之前调用。

注意：（1）

if (savedInstanceState != null) {
			mTheme = savedInstanceState.getInt(THEME);
			switchTheme(mTheme);
		}

这部分代码要在setContentView(R.layout.activity_main)代码之前调用，否则改变不了主题。

（2）recreate()方法是在Android3.0引入的，所以假设在3.0之前使用会出现错误。例如以下图所看到的：