Android error:<identifier>预期

Question

在这个SensorTestActivity.java中，Android将R标记为红色：

package szabojanos.accelerometer;
import android.app.Activity;
import android.graphics.Color;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Toast;


public class SensorTestActivity extends Activity implements SensorEventListener {
private SensorManager sensorManager;
private boolean color = false;
private View view;
private long lastUpdate;


@Override
public void onCreate(Bundle savedInstanceState) {
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    view = findViewById(R.id.textview);
    view.setBackgroundColor(Color.GREEN);

    sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
    lastUpdate = System.currentTimeMillis();
}

@Override
public void onSensorChanged(SensorEvent event) {
    if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
        getAccelerometer(event);
    }

}

private void getAccelerometer(SensorEvent event) {
    float[] values = event.values;
    float x = values[0];
    float y = values[1];
    float z = values[2];

    float accelationSquareRoot = (x * x + y * y + z * z)
            / (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH);
    long actualTime = event.timestamp;
    if (accelationSquareRoot >= 2) //
    {
        if (actualTime - lastUpdate < 200) {
            return;
        }
        lastUpdate = actualTime;
        Toast.makeText(this, "Az eszköz fel volt rázva", Toast.LENGTH_SHORT)
                .show();
        if (color) {
            view.setBackgroundColor(Color.GREEN);
        } else {
            view.setBackgroundColor(Color.RED);
        }
        color = !color;
    }
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {

}

@Override
protected void onResume() {
    super.onResume();
    sensorManager.registerListener(this,
            sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
            SensorManager.SENSOR_DELAY_NORMAL);
}

@Override
protected void onPause() {
    super.onPause();
    sensorManager.unregisterListener(this);
}

这是android_sensor_test.xml布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:orientation="vertical" >

<TextView
    android:id="@+id/textview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

</LinearLayout>

我遵循本教程：http://www.vogella.com/tutorials/AndroidSensor/article.html#tutorial-accelerometer任何帮助都将不胜感激。

Answer 1

清洁-首先重建项目，然后Import

基本语法

import szabojanos.accelerometer.R;

FYI

在requestWindowFeature之后调用super.onCreate.

    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);// Call this after super.onCreate
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);

Answer 2

您缺少了.R导入。您可以通过在红线上按组合ALT+ENTER并选择import yourpackage.R来自动修复这个问题。

Answer 3

导入您的Package.R，如果您的xml文件中有任何问题，请解决，然后尝试清理和构建。