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。

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，感谢你的阅读和对的支持。