子线程Handler sendMessage 报错 Attempt to invoke virtual method '

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03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: FATAL EXCEPTION: main
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: Process: tech.androidstudio.tulingdemo, PID: 16029
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: java.lang.IllegalStateException: Could not execute method for android:onClick
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:275)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.view.View.performClick(View.java:4761)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.view.View$PerformClick.run(View.java:19767)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Looper.loop(Looper.java:135)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5310)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:372)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: Caused by: java.lang.reflect.InvocationTargetException
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:372)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.view.View.performClick(View.java:4761)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.view.View$PerformClick.run(View.java:19767)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Looper.loop(Looper.java:135)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5310)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:372)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.os.Handler.sendMessage(android.os.Message)' on a null object reference
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at tech.androidstudio.tulingdemo.MainActivity.btnSendMessage(MainActivity.java:65)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:372)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.view.View.performClick(View.java:4761)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.view.View$PerformClick.run(View.java:19767)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.os.Looper.loop(Looper.java:135)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5310)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:372)
03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)

03-17 08:10:18.760 16029-16029/tech.androidstudio.tulingdemo E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)

原因分析：

子线程handler 报错，是因为没有启动子线程就开始使用了。

解决办法：

在onCreate方法中启动Thread，千万别忘了Thread里面的this 参数，不然还会报错。

Thread thread = new Thread(this);        thread.start();

public class MainActivity extends AppCompatActivity implements Runnable {private EditText mEditText;    private ListView mListView;    private List<String> mData;    private ListViewAdapter mAdapter;    private Handler subHandler;    private Handler mainHandler;    private final int MAIN_HANDLER_ADD=98;    private final int SUB_HANDLER_ADD=998;    private final int SUB_HANDLER_EXIT=199;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mEditText=(EditText)findViewById(R.id.editText);        mListView=(ListView)findViewById(R.id.listView);        mData = new ArrayList<>();        mAdapter = new ListViewAdapter(mData,this);        mListView.setAdapter(mAdapter);        mainHandler = new Handler(){            @Override            public void handleMessage(Message msg) {                super.handleMessage(msg);                int what = msg.what;                switch (what){                    case MAIN_HANDLER_ADD:                        String msg_reply = (String)msg.obj;                        mData.add(msg_reply);                        mAdapter.notifyDataSetChanged();                        break;                }            }        };        //千万别忘了启动子线程，不然会报错        //Attempt to invoke virtual method 'boolean android.os.Handler.sendMessage(android.os.Message)' on a null object reference        Thread thread = new Thread(this);        thread.start();    }    public void btnSendMessage(View view) {        String message_send = mEditText.getText().toString();        if(message_send!=null){            mData.add(message_send);            mAdapter.notifyDataSetChanged();            //将要发送的消息发送给子线程,(给子线程的handler)，因为耗时操作不能在主线程进行            // 然后子线程请求数据再返回给主线程（主线程的 handler），因为 子线程不能修改界面的UI            Message message = Message.obtain();            message.what=SUB_HANDLER_ADD;            message.obj=message_send;            subHandler.sendMessage(message);//之前报错的位置是这一步        }    }    @Override    public void run() {        //绑定 当前线程的Looper        Looper.prepare();            subHandler= new Handler(){                @Override                public void handleMessage(Message msg) {                    super.handleMessage(msg);                    int what = msg.what;                    switch (what){                        case SUB_HANDLER_ADD:                            //获取发送的消息，然后通过HttpUtils来发送，并且得到返回值，                            //把这个返回值 再给主线程的 handler来处理。                            //先写一个模拟数据 ，例如"收到了"发送给主线程。                            Message message = Message.obtain();                            message.what=MAIN_HANDLER_ADD;                            message.obj="收到了";                            mainHandler.sendMessage(message);                            break;                        case SUB_HANDLER_EXIT:                            //在onDestroy里面停止这个Looper                            Looper looper = Looper.myLooper();                            looper.quit();                            break;                    }                }            };        //不停的循环 ，就像是while一样。        Looper.loop();    }}

给我老师的人工智能教程打call！http://blog.csdn.net/jiangjunshow

子线程Handler sendMessage 报错 Attempt to invoke virtual method '

给我老师的人工智能教程打call！http://blog.csdn.net/jiangjunshow

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