Android 简单回调示例

阳光穿透心脏的1/2处 2022-07-18 06:15 172阅读 0赞

**需要完成效果：点击第一个界面文字跳到第二个界面，点击第二个界面按钮跳回到第一个界面，**

**同时第一个界面的文字发生改变。**

**第一个界面：**

**布局：**

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.example.administrator.jreduch08.OneActivity">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="等待结果"
        android:textSize="20sp"
        android:gravity="center"
        android:id="@+id/tv"
        android:clickable="true"/>
    </RelativeLayout>

代码：

package com.example.administrator.jreduch08;
    
    import android.content.Intent;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.TextView;
    
    public class OneActivity extends AppCompatActivity implements TwoActivity.CallBack{
        private TextView tv;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_one);
            tv= (TextView) findViewById(R.id.tv);
            TwoActivity.setCallBack(this);
            tv.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent=new Intent(getBaseContext(),TwoActivity.class);
                    startActivity(intent);
                }
            });
        }
        @Override
        public void changeText(String resultStr) {
            tv.setText(resultStr);
        }
    }

第二个界面：

**布局：**

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.example.administrator.jreduch08.TwoActivity">
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="返回结果"
        android:id="@+id/back"/>
    </RelativeLayout>

代码：

package com.example.administrator.jreduch08;
    
    import android.content.Context;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    
    public class TwoActivity extends AppCompatActivity {
        private Button back;
        private static CallBack callBack;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_two);
            back= (Button) findViewById(R.id.back);
            back.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    callBack.changeText("这就是回调，厉害了");
                    finish();
                }
            });
        }
        public static void setCallBack(Context context){
            callBack= (CallBack) context;
        }
        public interface CallBack{
            public void changeText(String resultStr);
        }
    }

完成效果：

**![Center][]  
  
![Center 1][]  
![Center 2][]**

[Center]: /images/20220717/62d645aeb061438993f49189ee9daacd.png
[Center 1]: /images/20220717/715b581e325044b2b80ed0b4475f0131.png
[Center 2]: /images/20220717/55366ccdce8a4a5ca6f2a7f4ab508941.png