java - Android 的东西 - 如何在命令 mLedGpio.setValue(true) 后保持 LED 不间断

Question

我完成了这个项目：sample-button 但是我需要将其更改为在按下按钮时保持 LED 亮着，并在再次按下按钮后将其熄灭。

我该怎么做？

Answer 1

删除onKeyDown覆盖方法中的代码并更改setLedValue为：

private void setLedValue(boolean value) {
    try {
        mLedGpio.setValue(!mLedGpio.getValue());
    } catch (IOException e) {
        Log.e(TAG, "Error updating GPIO value", e);
    }
}

（您最好删除 onKeyDown 而不是 onKeyUp 以获得更好的用户体验。从用户体验的角度来看，在释放键时更改某些内容比在第一次按下时执行操作要好得多。）

---

如果你想看到整个班级发生了变化，它看起来像这样：

public class ButtonActivity extends Activity {

    private Gpio mLedGpio;
    private ButtonInputDriver mButtonInputDriver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        PeripheralManager pioService = new PeripheralManager.getInstance();
        try {
            mLedGpio = pioService.openGpio(BoardDefaults.getGPIOForLED());
            mLedGpio.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW);

            mButtonInputDriver = new ButtonInputDriver(
                    BoardDefaults.getGPIOForButton(),
                    Button.LogicState.PRESSED_WHEN_LOW,
                    KeyEvent.KEYCODE_SPACE);
            mButtonInputDriver.register();
        } catch (IOException e) {
            throw new IllegalStateException("Error configuring GPIO pins", e);
        }
    }

    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_SPACE) {
            toggleLedValue();
            return true;
        }    
        return super.onKeyUp(keyCode, event);
    }

    /**
     * Update the value of the LED output.
     */
    private void toggleLedValue() {
        try {
            mLedGpio.setValue(!mLedGpio.getValue());
        } catch (IOException e) {
            Log.e(TAG, "Error updating GPIO value", e);
        }
    }

    @Override
    protected void onDestroy(){
        super.onDestroy();

        mButtonInputDriver.unregister();
        try {
            mButtonInputDriver.close();
        } catch (IOException e) {
            Log.e(TAG, "Error closing Button driver", e);
        }

        try {
           mLedGpio.close();
        } catch (IOException e) {
           Log.e(TAG, "Error closing LED GPIO", e);
        } 
   }  
}

Answer 2

尝试在ButtonActivity.java中替换以下回调方法

static boolean mToggle ;
@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_SPACE) {
            // Turn on the LED
            mToggle = !mToggle;
            setLedValue(mToggle);
            return true;
        }

        return super.onKeyDown(keyCode, event);
    }

    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_SPACE) {
            // Turn off the LED
           // setLedValue(false);
            return true;
        }

        return super.onKeyUp(keyCode, event);
}