Android中如何使用基于回调的事件处理

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1. 编写接口

   public interface DownloadCallback {
   
       void startDownload();
   
       void updateProgress(int progress);
   
       void finishedDownload();
   }
   

2. 编写事件源

   public class HttpUtil {
       private Timer mTimer;
       private TimerTask mTimerTask;
       private DownloadCallback mCallback;
       public void setCallback(DownloadCallback callback) {
           this.mCallback = callback;
       }
       public HttpUtil() {
           mTimer = new Timer();
           mTimerTask = new TimerTask() {
               int i = 0;
               @Override
               public void run() {
                   if (i < 100) {
                       mCallback.updateProgress(i++);
                   } else {
                       mCallback.finishedDownload();
                       mTimer.cancel();
                   } } };
       }
       public void donwload() {
           mCallback.startDownload();
           mTimer.schedule(mTimerTask, 1000, 50);
       }}
   

3. 设置事件

   public class DownloadActivity extends Activity implements DownloadCallback {
       private HttpUtil mHttpUtil;
       private final String TAG = DownloadActivity.class.getSimpleName();
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_download);
   	  mHttpUtil = new HttpUtil();
           mHttpUtil.setCallback(this);
       }
       @Override
       public void startDownload() {
           Log.i(TAG, "开始下载");
       }
       @Override
       public void updateProgress(int progress) {
           Log.i(TAG, "已下载" + progress + "%");
       }
       @Override
       public void finishedDownload() {
           Log.i(TAG, "下载完成");
       }
   }
   

4. 触发事件

      @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_download);
   
           downloadBtn = findViewById(R.id.btn_download);
           mHttpUtil = new HttpUtil();
           mHttpUtil.setCallback(this);
   
           downloadBtn.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View v) {
                   mHttpUtil.donwload();
               }
           });
       }
   

5. 查看效果