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我是java android studio新手。目前我正在做一个项目，即将图像从相机转换为二进制。我遵循这个链接的所有步骤（Android: Convert Grayscale to Binary Image）。然后，运行时的问题与此链接相同（Android : Converting imageview to bitmap, to grayscale, bitmap to imageview）。我解决了这个问题，但仍然无法在我的设备上运行，它显示通知不幸的是，应用程序已停止。该logcat的结果显示：Java Android Studio：将图像从相机转换为Binary
04-24 16:46:18.573 22890-22890/? I/art: Late-enabling -Xcheck:jni
04-24 16:46:18.813 22890-22890/com.example.gabriel.image D/AndroidRuntime: Shutting down VM
04-24 16:46:18.823 22890-22890/com.example.gabriel.image E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.gabriel.image, PID: 22890
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gabriel.image/com.example.gabriel.image.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.graphics.Bitmap android.graphics.drawable.BitmapDrawable.getBitmap()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2303)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
at android.app.ActivityThread.access$800(ActivityThread.java:147)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1283)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5234)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:909)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:704)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.graphics.Bitmap android.graphics.drawable.BitmapDrawable.getBitmap()' on a null object reference
at com.example.gabriel.image.MainActivity.onCreate(MainActivity.java:36)
at android.app.Activity.performCreate(Activity.java:5984)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2256)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
at android.app.ActivityThread.access$800(ActivityThread.java:147)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1283)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5234)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:909)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:704)
这里是我的全部编码：
public static final int REQUEST_CAPTURE = 1;
ImageView result_photo;
Button Binary;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button click = (Button) findViewById(R.id.BCapture);
result_photo = (ImageView) findViewById(R.id.imageView);
Binary = (Button) findViewById(R.id.btnBinary);
BitmapDrawable drawable = (BitmapDrawable) result_photo.getDrawable();
final Bitmap result_photoBitmap = drawable.getBitmap();
Binary.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
//convert bitmap to grayscale
Bitmap result_photoNew;
result_photoNew = toGrayscale(result_photoBitmap);
//Convert to Binary
result_photoNew = toBinary(result_photoNew);
//convert bitmap to imageview
ImageView img_binary;
img_binary = (ImageView) findViewById(R.id.imageView2);
img_binary.setImageBitmap(result_photoNew);
}
});
if (!hasCamera()) {
click.setEnabled(false);
}
}
public boolean hasCamera() {
return getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_ANY);
}
public void launchCamera(View v) {
Intent i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(i, REQUEST_CAPTURE);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == REQUEST_CAPTURE && resultCode == RESULT_OK) {
Bundle extras = data.getExtras();
Bitmap photo = (Bitmap) extras.get("data");
getResizedBitmap(photo, 120, 120);
result_photo.setImageBitmap(photo);
}
}
public Bitmap getResizedBitmap(Bitmap bm, int newHeight, int newWidth) {
int width = bm.getWidth();
int height = bm.getHeight();
float scaleWidth = ((float) newWidth)/width;
float scaleHeight = ((float) newHeight)/height;
// CREATE A MATRIX FOR THE MANIPULATION
Matrix matrix = new Matrix();
// RESIZE THE BIT MAP
matrix.postScale(scaleWidth, scaleHeight);
// RECREATE THE NEW BITMAP
Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, false);
return resizedBitmap;
}
public Bitmap toGrayscale(Bitmap bmpOriginal){
int width, height;
height = bmpOriginal.getHeight();
width = bmpOriginal.getWidth();
Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
Canvas c = new Canvas(bmpGrayscale);
Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
paint.setColorFilter(f);
c.drawBitmap(bmpOriginal, 0, 0, paint);
return bmpGrayscale;
}
public Bitmap toBinary(Bitmap bmpOriginal) {
int width, height, threshold;
height = bmpOriginal.getHeight();
width = bmpOriginal.getWidth();
threshold = 127;
//final Bitmap bmpBinary = null;
Bitmap bmpBinary = Bitmap.createBitmap(bmpOriginal);
for(int x = 0; x < width; ++x) {
for(int y = 0; y < height; ++y) {
// get one pixel color
int pixel = bmpOriginal.getPixel(x, y);
int red = Color.red(pixel);
int green = Color.green(pixel);
int blue = Color.blue(pixel);
//get grayscale value
int gray = (int)(red * 0.3 + green * 0.59 + blue *0.11);
//get binary value
if(gray < threshold){
bmpBinary.setPixel(x, y, 0xFF000000);
} else{
bmpBinary.setPixel(x, y, 0xFFFFFFFF);
}
}
}
return bmpBinary;
}
plz帮助我。
请添加activity_main.xml代码 – USKMobility
在标题或“android-studio”标签中不需要“Android Studio”，因为问题与Android Studio IDE本身无关，而与一般的Android编程无关。 –
看起来像result_photo是空的，检查ID匹配您的布局XML ID。此外，您的调整大小的位图方法返回一个位图对象，但是当你调用它时，你不坐它返回的位图。 – seanAshmore