在安卓的开发过程中,经常需要对之前的数据进行保存。这个时候就需要进行保护现场的操作,该操作主要是重写了onSaveInstanceState和onRestoreInstanceState两个函数。
onSaveInstanceState,保存数据
活动生命周期的执行顺序:
onPause-onSaveInstanceState-onStop-onDestroy
onRestoreInstanceState,恢复数据
活动生命周期的执行顺序:
onStart-onRestoreInstanceState-onResume
下面这个例子就以手机横竖屏为例,保护了背景颜色这一数据。
package com.example.hjw.androidday0602; import android.graphics.Color; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.LinearLayout; import android.widget.Toast; import java.util.Random; public class MainActivity extends AppCompatActivity { private LinearLayout linearLayout; private Button button; String r,g,b,c; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); linearLayout = (LinearLayout)findViewById(R.id.l1); button = (Button)findViewById(R.id.b1); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Random random = new Random(); r = Integer.toHexString(random.nextInt(256)).toUpperCase(); g = Integer.toHexString(random.nextInt(256)).toUpperCase(); b = Integer.toHexString(random.nextInt(256)).toUpperCase(); r = r.length()==1 ? "0" + r : r ; g = g.length()==1 ? "0" + g : g ; b = b.length()==1 ? "0" + b : b ; c="#"+r+b+g; Toast.makeText(MainActivity.this,c,Toast.LENGTH_SHORT).show(); linearLayout.setBackgroundColor(Color.parseColor(c)); } }); } // 保存数据 // 参数为Bundle类型,用于存储数据 @Override protected void onSaveInstanceState(Bundle outState) { // TODO Auto-generated method stub super.onSaveInstanceState(outState); if (c!=null){ outState.putString("color", c); } } // 恢复数据 // 参数为Bundle类型,用于读取数据 @Override protected void onRestoreInstanceState(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onRestoreInstanceState(savedInstanceState); c = savedInstanceState.getString("color"); linearLayout.setBackgroundColor(Color.parseColor(c)); } // 重新将值恢复 @Override protected void onResume() { // TODO Auto-generated method stub super.onResume(); Toast.makeText(MainActivity.this,c,Toast.LENGTH_SHORT).show(); } }
前台代码
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/l1" 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.hjw.androidday0602.MainActivity"> <Button android:id="@+id/b1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="跳转"/> </LinearLayout>
运行效果:
时间: 2024-10-06 13:39:05