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簡書 沿路旅程如歌蛻變

點這裡

利用handler.postDelay()方法來實現定時器計時

下面的程式碼實現了6s倒計時,計時後,自動停止計時並移除runnable.

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    private CountDownTimer mTimer;
    private int time=6;
    private TextView textView;
    private Handler handler=new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView=findViewById(R.id.text);
        initHandler();
    }

    private void initHandler() {
        Runnable runnable=new Runnable() {
            @Override
            public void run() {
                Log.i(TAG, "run: time="+time);
                if (time!=0){
                    handler.postDelayed(this,1000);
                    time--;
                    textView.setText(String.valueOf(time));
                }else {
                    handler.removeCallbacks(this);
                }
            }
        };
        handler.post(runnable);
    }

@Override
    protected void onDestroy() {
        handler.removeCallbacksAndMessages(null);
        super.onDestroy();
    }
}
 

對handler執行緒的管理,啟動和銷燬

執行緒的啟動和銷燬(防止記憶體洩漏)

        //正常啟動
        handler.post(runnable);
        //延時1000ms啟動
        handler.postDelayed(runnable,1000);
        
        //銷燬指定執行緒
        handler.removeCallbacks(runnable);
        //清空所有訊息和執行緒
        handler.removeCallbacksAndMessages(null);