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")

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

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

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

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。

以上相关知识点如果还有什么疏漏大家可以直接联系小编，感谢你的阅读和对w3xue的支持。