Android Studio屏幕方向以及UI界面状态的保存代码详解

package com.example.orientation; import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.TextView; import androidx.appcompat.app.AppCompatActivity; public class MainActivity extends AppCompatActivity {/*  = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =  本实例主要学习，屏幕翻转时，界面如何自适应，创建横屏布局  1.禁止切换横屏：在 AndroidManifest.xml-->application->activity->中设置如下代码（android:screenOrientation="portrait"）   <activity android:name=".MainActivity" android:screenOrientation="portrait" >  2. 创建 Landscape 布局，横屏时，会自动加载 Landscape 的布局界面（清单文件中，注意去掉 android:screenOrientation="portrait" ）  3. 翻转屏幕时，保存窗口控件的状态值;   = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */  Button button;  TextView textView;   String TAG = "myTag";   @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);     button = findViewById(R.id.button );    textView = findViewById(R.id.textView);     //如果State中的值不为空，如果有相应的这个组件的值，则读取出来赋值上去    if(savedInstanceState !=null)    {      String s = savedInstanceState.getString("key");      textView.setText(s);    }     button.setOnClickListener(new View.OnClickListener() {      @Override      public void onClick(View view) {        textView.setText(button.getText());      }    });  }   @Override  protected void onDestroy() {    super.onDestroy();    Log.d(TAG,"onDestroy:");  }   @Override  //将 textView 中的值，先保存到 outState 中（键值对）  public void onSaveInstanceState(Bundle outState) {    super.onSaveInstanceState(outState);    outState.putString("key",textView.getText().toString());  }}

<TextView    android:id="@+id/textview"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:gravity="center"    android:text="This is a TextView"    android:textColor="#00ff00"    android:textSize="24sp" />

<Button    android:id="@+id/button"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:text="Button"    android:textAllCaps="false"/>

<EditText    android:id="@+id/edittext"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:hint="HelloWorld"    android:maxLength="20"    android:maxLines="1" />