HandlerThread – 蓝天白云

１．什么场景下需要使用HandlerThread

1). 比较耗时，不易于放在主线程中执行的操作（不考虑第２点使用其他线程方式也可以）

2). 有多个耗时操作需要后台执行（如果不嫌麻烦也可以考虑使用多个TThread）

２．HandlerThread的使用步骤

1). 创建HandlerThread对象

2). 执行start方法，启动HandlerThread的Looper循环

3). 在主线程中创建Handler对象并引用HandlerTherad的looper

4). 在Handler对象中加入各种消息的处理

5). 在需要的时候给步骤３创建的Handler对象发送消息

6). 不再需要HandlerThread的时候调用quit或者quitSafely停止HandlerThread

示例代码如下(没做各种错误处理，仅供参考)：

public class MainActivity extends AppCompatActivity {

    private Handler handler;
    private HandlerThread myHandlerThread ;
    private final int MSG_DOWNLOAD = 1;
    private final int MSG_DOWNLOAD2 = 2;

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

        myHandlerThread = new HandlerThread("test_thread");
        // 这一步很重要
        myHandlerThread.start();
        handler = new Handler(myHandlerThread.getLooper()){
            @Override
            public void handleMessage(Message msg) {
                OkHttpClient client = new OkHttpClient();
                super.handleMessage(msg);
                switch (msg.what){
                    case MSG_DOWNLOAD:

                        Request request = new Request.Builder()
                                .url("http://baidu.com")
                                .build();

                        try {
                            Response response = client.newCall(request).execute();
                            Log.d("DOWNLOAD", response.body().string());
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                        break;
                    case MSG_DOWNLOAD2:
                        Request request1 = new Request.Builder()
                                .url("http://bcoder.com")
                                .build();

                        try {
                            Response response = client.newCall(request1).execute();
                            Log.d("DOWNLOAD", response.body().string());
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                        break;
                }
            }
        }; ;
    }

    public void onDownload1Click(View v){
        handler.sendEmptyMessage(MSG_DOWNLOAD);
    }

    public void onDownload2Click(View v){
        handler.sendEmptyMessage(MSG_DOWNLOAD2);
    }

    public void onQuitClick(View v){
        myHandlerThread.quit();
    }
}

public class MainActivity extends AppCompatActivity {

private Handler handler;

private HandlerThread myHandlerThread ;

private final int MSG_DOWNLOAD = 1;

private final int MSG_DOWNLOAD2 = 2;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

myHandlerThread = new HandlerThread("test_thread");

// 这一步很重要

myHandlerThread.start();

handler = new Handler(myHandlerThread.getLooper()){

@Override

public void handleMessage(Message msg) {

OkHttpClient client = new OkHttpClient();

super.handleMessage(msg);

switch (msg.what){

case MSG_DOWNLOAD:

Request request = new Request.Builder()

.url("http://baidu.com")

.build();

try {

Response response = client.newCall(request).execute();

Log.d("DOWNLOAD", response.body().string());

} catch (IOException e) {

e.printStackTrace();

}

break;

case MSG_DOWNLOAD2:

Request request1 = new Request.Builder()

.url("http://bcoder.com")

.build();

try {

Response response = client.newCall(request1).execute();

Log.d("DOWNLOAD", response.body().string());

} catch (IOException e) {

e.printStackTrace();

}

break;

}

}; ;

}

public void onDownload1Click(View v){

handler.sendEmptyMessage(MSG_DOWNLOAD);

}

public void onDownload2Click(View v){

handler.sendEmptyMessage(MSG_DOWNLOAD2);

}

public void onQuitClick(View v){

myHandlerThread.quit();

}

测试时多次点击Download1和Download2按钮，handler对象就会按点击的顺序多次下载网页baid.com和bcoder.com

3. 要不要像Thread那样写一个HandlerThread的子类？

完全没有必要，因为真正程序执行部分都在handler的消息处理里

4. quit和quitSafely的区别？

5. HandlerThread的其它特点

1). HandlerThread中的多个操作是串行按序执行的，即任务１＼任务２＼任务３．．．．，所以如果你想尽早的获得运行结果，不建议使用HandlerThread这种方式

6. 测试代码下载

LocaleTest