Question

我想在我的secondeActivity中嵌入我的加速度计类，但我总是得到一个强制转换异常这是我的加速计类：

package com.example.lincision;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;

public class Accelerometer implements SensorEventListener {

    private float xAxis;
    private float yAxis;
    private float zAxis;
    private float lastX, lastY, lastZ;

    public float getX() {
        return this.xAxis;
    }

    public float getY() {
        return this.yAxis;
    }

    public float getZ() {
        return this.zAxis;
    }

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

    }

    @Override
    public void onSensorChanged(SensorEvent event) {

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

    }

}

在这里，你看到我的第二个活动根本不起作用，也许有些是我的理想必须改变。

package com.example.lincision;

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

import com.javacodegeeks.androidaccelerometerexample.R;

public class SecondActivity extends Activity {



    TextView outputX;
    TextView outputY;
    TextView outputZ;

    SensorManager manager;
    Sensor accelerometer;

    SensorManager sensorManager;


    TextView currentX, currentY, currentZ;

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

    initializeViews();
    displayCleanValues();
    // display the current x,y,z accelerometer values
    displayCurrentValues();

    sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

    accelerometer = sensorManager
            .getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
    sensorManager.registerListener((SensorEventListener) acc,
            accelerometer, SensorManager.SENSOR_DELAY_NORMAL);

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

    }

    private float deltaX = acc.getX();
    private float deltaY = acc.getY();
    private float deltaZ = acc.getZ();



    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));
    }

}

这是我的错误消息：

01-14 12:36:58.751: E/AndroidRuntime(18696): java.lang.RuntimeException: Unable to start activity       ComponentInfo{com.javacodegeeks.androidaccelerometerexample/com.example.lincision.SecondActivity}:      java.lang.ClassCastException: com.example.lincision.SecondActivity cannot be cast to android.hardware.SensorEventListener
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2394)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2452)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.app.ActivityThread.access$900(ActivityThread.java:172)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1302)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.os.Handler.dispatchMessage(Handler.java:102)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.os.Looper.loop(Looper.java:136)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at android.app.ActivityThread.main(ActivityThread.java:5586)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at java.lang.reflect.Method.invokeNative(Native Method)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at java.lang.reflect.Method.invoke(Method.java:515)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
01-14 12:36:58.751: E/AndroidRuntime(18696):    at dalvik.system.NativeStart.main(Native Method)
01-14 12:36:58.751: E/AndroidRuntime(18696): Caused by: java.lang.ClassCastException: com.example.lincision.SecondActivity cannot be cast to android.hardware.SensorEventListener

Answer 1

SensorManager.registerListener将SensorEventListener个对象作为参数，而您未在SensorEventListener中实施SecondActivity。

因为您正在SensorEventListener中实现Accelerometer，所以将acc作为registerListener中的第一个参数传递：

sensorManager.registerListener((SensorEventListener)acc, accelerometer,
                SensorManager.SENSOR_DELAY_NORMAL);

Answer 2

引起：java.lang.ClassCastException： com.example.lincision.SecondActivity无法强制转换为 android.hardware.SensorEventListener

如错误所示，您正在将Activity转换为SensorEventListener。这是导致问题的一行：

sensorManager.registerListener((SensorEventListener) this, accelerometer,
            SensorManager.SENSOR_DELAY_NORMAL);

请勿在registerListener中将此强制转换为SensorEventListener，因为此指的是SecondActivity，并且它没有实现SensorEventListener。相反，传递 acc ，这是Accelerometer实现SensorEventListener的对象，而SensorEventListener又是registerListener所需的第一个参数：

sensorManager.registerListener((SensorEventListener)acc, accelerometer,
            SensorManager.SENSOR_DELAY_NORMAL);

Accelerometer Class的Android问题

2 个答案: