在子线程中更新UI

墨蓝 2022-06-12 14:57 210阅读 0赞

**运行截图**  
![这里写图片描述][SouthEast]  
**MainActivity.java**

package csdn.example.com.notification.AndroidThreadTest;
    
    import android.os.Handler;
    import android.os.Message;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.TextView;
    
    import csdn.example.com.notification.R;
    
    public class Main8Activity extends AppCompatActivity implements View.OnClickListener {
        
    
        //异步消息处理机制
        public static final int UPDATA_TEXT = 1;
    
        private Handler handler = new Handler(){
            @Override
            public void handleMessage(Message msg) {
                switch (msg.what){
                    case UPDATA_TEXT:
                        //在这里可以进行UI操作
                        textView.setText("Nice to meet you");
                        break;
                    default:
                        break;
                }
            }
        };
        TextView textView;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main8);
            textView = (TextView) findViewById(R.id.change_text);
            Button changeText = (Button) findViewById(R.id.change_text);
            changeText.setOnClickListener(this);
    
        }
    
        @Override
        public void onClick(View v) {
            switch (v.getId()){
                case R.id.change_text:
                    new Thread(new Runnable() {
                        @Override
                        public void run() {
                            Message message = new Message();
                            message.what = UPDATA_TEXT;
                            handler.sendMessage(message); //将Message对象送出去
                        }
                    }).start();
                    break;
                default:
                    break;
            }
        }
    }

**activity\_main.xml**

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout android:layout_width="match_parent"
        android:layout_height="match_parent"
        xmlns:android="http://schemas.android.com/apk/res/android">
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/change_text"
            android:text="Change Text"
            />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/text"
            android:layout_centerInParent="true"
            android:text="Hello world"
            android:textSize="20sp"
            />
    </RelativeLayout>

[SouthEast]: /images/20220612/969670243f984b6e91881a0d3e97ee95.png