Android的進程Hnadler與AsyncTask

概述：

不能在非UI線程中操完成UI線程中的操作；
服務必須在manifests中註冊。

代碼

進程

完成一個倒計時

public class TestThread extends Activity {
    private Button mTimeCountButton;
    private int count;
    private static final int TIME_DESC = 0x23;
    private Handler mHandler;
    private Message message;
    //方法2：在Handler中完成
//    private Handler handler = new Handler() {
//        @Override
//        public void handleMessage(Message msg) {
//            switch (msg.what){
//                case TIME_DESC:
//                    mTimeCountButton.setText(count+"秒");
//                    count--;
//                    try {
//                        Thread.sleep(1000);
//                    } catch (InterruptedException e) {
//                        e.printStackTrace();
//                    }
//                    handler.sendEmptyMessage(TIME_DESC);
//                    break;
//                default:
//                    break;
//            }
//        }
//    };

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

        message = new Message();
        mTimeCountButton = (Button) findViewById(R.id.button_time_count);
        mTimeCountButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MyThread thread = new MyThread();
                thread.start();
                //方法1：在監聽函數中
//                count = 60;
//            handler.sendEmptyMessage(TIME_DESC);
//                new Thread(new Runnable() {
//                    @Override
//                    public void run() {
//                        while (count>0){
//                            Message msg = new Message();
//                            msg.obj = count+"秒";
//                            msg.what = TIME_DESC;
//                            handler.sendMessage(msg);
//                            try {
//                                Thread.sleep(1000);
//                            } catch (InterruptedException e) {
//                                e.printStackTrace();
//                            }
//                            count--;
//                        }
//                    }
//                }).start();
            }
        });
    }
    //方法3：用Looper完成
    class MyThread extends Thread {
        @Override
        public void run() {
            Looper.prepare();
            mHandler = new Handler() {
                @Override
                public void handleMessage(Message msg) {
                    Log.d("dd", "接受到主線程的消息");
                }
            };
            Looper.loop();
        }
    }
}

佈局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="倒計時"/>
    <Button
        android:id="@+id/button_time_count"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="60秒"/>
</LinearLayout>

AsyncTask

新建的Task繼承於AsyncTask需要實現三個方法：

public class TestAsycTask extends Activity {
    private ProgressBar mProgressBar;
    private Button mButton;
    private int count;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_async_task);

        mProgressBar = (ProgressBar) findViewById(R.id.progressBar_asyc);
        mButton = (Button) findViewById(R.id.button_asyc);
        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MyTask task = new MyTask();
                task.execute();
            }
        });
    }

    class MyTask extends AsyncTask<String,String,String>{

        @Override
        protected void onProgressUpdate(String... values) {
            super.onProgressUpdate(values);
            int count = Integer.parseInt(values[0]);
            mProgressBar.setProgress(count);
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            mButton.setText(s);
        }

        @Override
        protected String doInBackground(String... params) {
            while(count<101){
                count++;
                publishProgress(""+count);
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            return "全部完成";
        }
    }
}

佈局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <ProgressBar
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:id="@+id/progressBar_asyc"
        android:layout_gravity="center_horizontal"/>

    <Button
        android:id="@+id/button_asyc"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Start Download"/>
</LinearLayout>