Android Studio屏幕方向以及UI界面状态的保存代码详解
项目:Orientation
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()); } }
扩展学习:
UI界面设计
TextView
<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" />
要想使得文字居中,需要添加属性android:gravity="center",可选择的选项还有top、bottom、left、right、center等,center相当于center_vertical|center_horizontal。
使用android:textSize="24sp"指定文字大小,android:textColor="#00ff00"指定文字颜色。
Button
<Button android:id="@+id/button" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Button" android:textAllCaps="false"/>
在Android中,Button上面的文字默认英文全部大写,可以通过设置android:textAllCaps="false"改变
EditText
<EditText android:id="@+id/edittext" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="HelloWorld" android:maxLength="20" android:maxLines="1" />
通过设置hint属性可以得到提示文字,设置maxLines使得输入框中最大输入行数。
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