问题描述

创建handler对象指定一个Callback的代码报错

public class MainActivity extends Activity implements OnClickListener{
private TextView textView;
private ImageView imageView;
private int index;
private int images [] = {R.drawable.image1,R.drawable.image2,R.drawable.image3};
private MyRunnable runnable = new MyRunnable();
private Button button;

class Person{
    public int age;
    public String name;

    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return "name=" + name + " age=" + age;
    }
}

private Handler handler = new Handler(new Callback() {

    @Override
    public boolean handleMessage(Message msg) {
        // TODO Auto-generated method stub
        Toast.makeText(getApplicationContext(),"" + 1, 1).show();
        return false;
    }
}){
    public void handleMessage(Message msg){
        Toast.makeText(getApplicationContext(),"" + 2, 1).show();
    }
};

class MyRunnable implements Runnable{
    @Override
    public void run() {
        // TODO Auto-generated method stub
        index++;
        index = index % 3;
        imageView.setImageResource(images[index]);
        handler.postDelayed(runnable, 1000);
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    imageView = (ImageView) findViewById(R.id.imageView1);
    textView = (TextView) findViewById(R.id.textview);
    button = (Button) findViewById(R.id.button1);
    button.setOnClickListener(this);

    new Thread(){
        public void run() {
            try {
                Thread.sleep(2000);
                Message message = handler.obtainMessage();
                Person person = new Person();
                person.age = 12;
                person.name = "mike";
                message.obj = person;
                message.sendToTarget();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        };
    }.start();

    handler.postDelayed(runnable, 1000);

}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    handler.sendEmptyMessage(1);
}

}

按照学习视频打得，一模一样，还是报错。
private Handler handler = new Handler(new Callback() {

    @Override
    public boolean handleMessage(Message msg) {
        // TODO Auto-generated method stub
        Toast.makeText(getApplicationContext(),"" + 1, 1).show();
        return false;
    }
}){
    public void handleMessage(Message msg){
        Toast.makeText(getApplicationContext(),"" + 2, 1).show();
    }
};

搞不懂
problems报错信息：大概意思是handler没有这种定义的构造，第二个是handleMessage方法需要重写或实现。首先这个方法是视频上面大的，我是照葫芦画瓢。第二这个方法已经重写了，有Toast...
Description Resource    Path    Location    Type

The constructor Handler(new Callback(){}) is undefined MainActivity.java /handler_01/src/com/hao123/handler_01 line 35 Java Problem
Description Resource Path Location Type
The method handleMessage(Message) of type new Callback(){} must override or implement a supertype method MainActivity.java /handler_01/src/com/hao123/handler_01 line 38 Java Problem
我试过如果改一下标点符号就报个标点符号的错误 ，例如把最后一排括回来的大括号和分号删除
Description Resource Path Location Type
Syntax error, insert ";" to complete FieldDeclaration MainActivity.java /handler_01/src/com/hao123/handler_01 line 121 Java Problem
Description Resource Path Location Type
Description Resource Path Location Type
Syntax error, insert "}" to complete ClassBody MainActivity.java /handler_01/src/com/hao123/handler_01 line 121 Java Problem
但是这种报错是那种坑爹的报错，明显那个地方是要标点的

解决方案

把错误信息贴出来，看明白是什么错误

解决方案二：

搞了好久，晕死了。终于解决了
private Handler handler = new Handler(new Handler.Callback(){

    @Override
    public boolean handleMessage(Message msg) {
        // TODO Auto-generated method stub
        Toast.makeText(getApplicationContext(),"" + 1, 1).show();
        return false;
    }

这个方法应该有一个对象调用，java 是面向对象的。
有一点挺搞不懂的。视频上不报错，难道是this调用的。还是我们的版本的问题