Question

我的应用程序称为忠诚度应用程序当我使用调试模式在手机上运行代码时，应用程序因错误而崩溃：不幸的是，忠诚度应用程序已经停止。

继承我的logcat：

04-03 20:31:49.546: D/AndroidRuntime(30853): Shutting down VM
04-03 20:31:49.546: W/dalvikvm(30853): threadid=1: thread exiting with uncaught exception (group=0x41e18700)
04-03 20:31:49.546: E/AndroidRuntime(30853): FATAL EXCEPTION: main
04-03 20:31:49.546: E/AndroidRuntime(30853): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.loyaltyapp/com.example.loyaltyapp.Camera}: java.lang.NullPointerException
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.ActivityThread.access$700(ActivityThread.java:159)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.os.Looper.loop(Looper.java:137)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.ActivityThread.main(ActivityThread.java:5419)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at java.lang.reflect.Method.invokeNative(Native Method)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at java.lang.reflect.Method.invoke(Method.java:525)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at dalvik.system.NativeStart.main(Native Method)
04-03 20:31:49.546: E/AndroidRuntime(30853): Caused by: java.lang.NullPointerException
04-03 20:31:49.546: E/AndroidRuntime(30853):    at com.example.loyaltyapp.Camera.onCreate(Camera.java:47)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.Activity.performCreate(Activity.java:5372)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-03 20:31:49.546: E/AndroidRuntime(30853):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
04-03 20:31:49.546: E/AndroidRuntime(30853):    ... 11 more

继承我的代码：

camera.java

 package com.example.loyaltyapp;

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class Camera extends Activity {

// Activity request codes
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
public static final int MEDIA_TYPE_IMAGE = 1;
// directory name to store captured images and videos
private static final String IMAGE_DIRECTORY_NAME = "Hello Camera";

private Uri fileUri; // file url to store image/video

private ImageView imgPreview;
private Button btnCapturePicture;

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

    imgPreview = (ImageView) findViewById(R.id.imgPreview);
    btnCapturePicture = (Button) findViewById(R.id.btnCapturePicture);

    /*
     * Capture image button click event
     */
    btnCapturePicture.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // capture picture
            captureImage();
        }
    });


    // Checking camera availability
    if (!isDeviceSupportCamera()) {
        Toast.makeText(getApplicationContext(),
                "Sorry! Your device doesn't support camera",
                Toast.LENGTH_LONG).show();
        // will close the app if the device does't have camera
        finish();
    }
}

/**
 * Checking device has camera hardware or not
 * */
private boolean isDeviceSupportCamera() {
    if (getApplicationContext().getPackageManager().hasSystemFeature(
            PackageManager.FEATURE_CAMERA)) {
        // this device has a camera
        return true;
    } else {
        // no camera on this device
        return false;
    }
}

/*
 * Capturing Camera Image will lauch camera app requrest image capture
 */
private void captureImage() {
    Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

    fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);

    intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

    // start the image capture Intent
    startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
}

/*
 * Here we store the file url as it will be null after returning from camera
 * app
 */
@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

    // save file url in bundle as it will be null on scren orientation
    // changes
    outState.putParcelable("file_uri", fileUri);
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);

    // get the file url
    fileUri = savedInstanceState.getParcelable("file_uri");
}

/**
 * Receiving activity result method will be called after closing the camera
 * */
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // if the result is capturing Image
    if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE) {
        if (resultCode == RESULT_OK) {
            // successfully captured the image
            // display it in image view
            previewCapturedImage();
        } else if (resultCode == RESULT_CANCELED) {
            // user cancelled Image capture
            Toast.makeText(getApplicationContext(),
                    "User cancelled image capture", Toast.LENGTH_SHORT)
                    .show();
        } else {
            // failed to capture image
            Toast.makeText(getApplicationContext(),
                    "Sorry! Failed to capture image", Toast.LENGTH_SHORT).show();
        }
    }
}

/*
 * Display image from a path to ImageView
 */
private void previewCapturedImage() {
    try {
        imgPreview.setVisibility(View.VISIBLE);

        // bimatp factory
        BitmapFactory.Options options = new BitmapFactory.Options();

        // downsizing image as it throws OutOfMemory Exception for larger
        // images
        options.inSampleSize = 8;

        final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),
                options);

        imgPreview.setImageBitmap(bitmap);
    } catch (NullPointerException e) {
        e.printStackTrace();
    }
}


/**
 * ------------ Helper Methods ---------------------- 
 * */

/*
 * Creating file uri to store image/video
 */
public Uri getOutputMediaFileUri(int type) {
    return Uri.fromFile(getOutputMediaFile(type));
}

/*
 * returning image / video
 */
private static File getOutputMediaFile(int type) {

    // External sdcard location
    File mediaStorageDir = new File( Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
            IMAGE_DIRECTORY_NAME);

    // Create the storage directory if it does not exist
    if (!mediaStorageDir.exists()) {
        if (!mediaStorageDir.mkdirs()) {
            Log.d(IMAGE_DIRECTORY_NAME, "Oops! Failed create "
                    + IMAGE_DIRECTORY_NAME + " directory");
            return null;
        }
    }

    // Create a media file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
            Locale.getDefault()).format(new Date());
    File mediaFile;
    if (type == MEDIA_TYPE_IMAGE) {
        mediaFile = new File(mediaStorageDir.getPath() + File.separator
                + "IMG_" + timeStamp + ".jpg");
    } 
    else {
        return null;
    }

    return mediaFile;
}
 }

activity_camera.xml

   <LinearLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:baselineAligned="false"
android:orientation="horizontal"
tools:context="Camera" >

<LinearLayout
    android:layout_width="0dp"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    android:gravity="center"
    android:orientation="vertical" >

    <!-- Capture picture button -->

    <Button
        android:id="@+id/btnCapturePicture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:text="Take a Picture" 
        android:onClick="Camera.captureImage()"/>

</LinearLayout>

<LinearLayout
    android:layout_width="0dp"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    android:orientation="vertical"
    android:padding="10dp">

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Preview"
        android:padding="10dp"
        android:textSize="15dp"/>

    <!-- To display picture taken -->

    <ImageView
        android:id="@+id/imgPreview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="gone" />

</LinearLayout>

</LinearLayout>

LoyaltyApp清单

 <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.loyaltyapp"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="11"
    android:targetSdkVersion="19" />

<!-- Accessing camera hardware -->
<uses-feature android:name="android.hardware.camera" />

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

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.loyaltyapp.MainActivity"
        android:label="@string/app_name"
        android:uiOptions="splitActionBarWhenNarrow" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.example.loyaltyapp.Camera"
        android:label="@string/title_activity_camera" >
    </activity>

</application>

</manifest>

主要活动

public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

if(id == R.id.action_camera) {
        Intent k = new Intent(this, Camera.class);
        startActivity(k);
        return true;
}

}

Answer 1

首先，您没有相机许可将<uses-permission android:name="android.permission.CAMERA" />添加到您的清单文件中其次，请在崩溃时发布您的logcat输出。如果您不与我们分享详细信息，我们无法弄清楚出了什么问题。

更新：这是一个NPE。根据您的logcat，相机按钮（btnCapturePicture = (Button) findViewById(R.id.btnCapturePicture);）为空，因为您在onCreate方法中使用完全不同的布局。
您使用setContentView(R.layout.activity_main);，但您的btnCapturePicture在activity_camera.xml中的完全不同的布局中使用了您在camera.java文件的onCreate方法中的setContentView(R.layout.activity_camera);。

Answer 2

模拟器中有设置转到设置->应用程序->相机->权限允许所有选项

您完成了，就这样

祝你好运

相机应用程序无法正常工作（应用程序崩溃）错误：很遗憾应用程序已停止

继承我的代码：

2 个答案: