我的 Android 应用程序在模拟器中崩溃

Question

My app is crashing. I am trying to build an accelerometer based app. Though build is successful, it is not running in the Pixel Emulator. Where have I gone wrong?

I have been trying to find the error but am unsuccessful. I am attaching the run error message, the screenshot of the manifest file and the main code.

This is the error message:

The main code follows

package com.example.androidaccelerometerexample;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.app.Activity;
import android.text.Html;
import android.view.Menu;
import android.widget.TextView;

import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Vibrator;
import android.widget.TextView;

class Main extends Activity implements SensorEventListener {

    private float lastX, lastY, lastZ;

    private SensorManager sensorManager;
    private Sensor accelerometer;

    private float deltaXMax = 0;
    private float deltaYMax = 0;
    private float deltaZMax = 0;

    private float deltaX = 0;
    private float deltaY = 0;
    private float deltaZ = 0;

    private float vibrateThreshold = 0;

    private TextView currentX, currentY, currentZ, maxX, maxY, maxZ;

    public Vibrator v;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initializeViews();

        sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        if (sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER) != null) {
            // success! we have an accelerometer

            accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
            sensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);
            vibrateThreshold = accelerometer.getMaximumRange() / 2;
        } else {
            // fai! we dont have an accelerometer!
        }

        //initialize vibration
        v = (Vibrator) this.getSystemService(Context.VIBRATOR_SERVICE);

    }

    public void initializeViews() {
        currentX = (TextView) findViewById(R.id.currentX);
        currentY = (TextView) findViewById(R.id.currentY);
        currentZ = (TextView) findViewById(R.id.currentZ);

        maxX = (TextView) findViewById(R.id.maxX);
        maxY = (TextView) findViewById(R.id.maxY);
        maxZ = (TextView) findViewById(R.id.maxZ);
    }
    protected void onResume() {
        super.onResume();
        sensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);
    }

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

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

    }

    @Override
    public void onSensorChanged(@org.jetbrains.annotations.NotNull SensorEvent event) {

        // clean current values
        displayCleanValues();
        // display the current x,y,z accelerometer values
        displayCurrentValues();
        // display the max x,y,z accelerometer values
        displayMaxValues();

        // get the change of the x,y,z values of the accelerometer
        deltaX = Math.abs(lastX - event.values[0]);
        deltaY = Math.abs(lastY - event.values[1]);
        deltaZ = Math.abs(lastZ - event.values[2]);

        // if the change is below 2, it is just plain noise
        if (deltaX < 2)
            deltaX = 0;
        if (deltaY < 2)
            deltaY = 0;
        if ((deltaZ > vibrateThreshold) || (deltaY > vibrateThreshold) || (deltaX > vibrateThreshold)) {
            v.vibrate(50);
        }
    }

    public void displayCleanValues() {
        currentX.setText("0.0");
        currentY.setText("0.0");
        currentZ.setText("0.0");
    }

    // display the current x,y,z accelerometer values
    public void displayCurrentValues() {
        currentX.setText(Float.toString(deltaX));
        currentY.setText(Float.toString(deltaY));
        currentZ.setText(Float.toString(deltaZ));
    }

    // display the max x,y,z accelerometer values
    public void displayMaxValues() {
        if (deltaX > deltaXMax) {
            deltaXMax = deltaX;
            maxX.setText(Float.toString(deltaXMax));
        }
        if (deltaY > deltaYMax) {
            deltaYMax = deltaY;
            maxY.setText(Float.toString(deltaYMax));
        }
        if (deltaZ > deltaZMax) {
            deltaZMax = deltaZ;
            maxZ.setText(Float.toString(deltaZMax));
        }
    }
}

Answer 1

Your activity class needs to be public and not package-private.

Change class Main to public class Main .