第一步：  首先添加权限：

<uses-permission android:name="android.permission.WAKE_LOCK"></uses-permission>

  第二步：代码实现如下：

public class ScreenActivity extends Activity

   {
        PowerManager powerManager = null;
        WakeLock wakeLock = null;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            this.setContentView(R.layout.main);
            powerManager = (PowerManager)this.getSystemService(this.POWER_SERVICE);
            wakeLock = this.powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, "My Lock");
       }

       @Override
       protected void onResume() {
           super.onResume();
           wakeLock.acquire();
       }

       @Override
       protected void onPause() {
           super.onPause();
           wakeLock.release();
       }

   }