Question

我一直收到这个错误，我不知道为什么。我试过谷歌搜索但没有运气。

04-21 15：43：24.822 2461-2461 / com.example.s.myapplication D / AndroidRuntime：关闭VM 04-21 15：43：24.823 2461-2461 / com.example.s.myapplication E / AndroidRuntime：FATAL EXCEPTION：main 处理：com.example.s.myapplication，PID：2461 java.lang.RuntimeException：将结果ResultInfo {who = null，request = 1，result = -1，data = null}传递给activity {com.example.s.myapplication / com.example.s.myapplication.MainActivity}： java.lang.NullPointerException：尝试在空对象引用上调用虚方法'void android.widget.ImageView.setImageBitmap（android.graphics.Bitmap）' 在android.app.ActivityThread.deliverResults（ActivityThread.java:3539）在android.app.ActivityThread.handleSendResult（ActivityThread.java:3582）在android.app.ActivityThread.access $ 1300（ActivityThread.java:144）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1327）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5221） at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:899）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:694）引起：java.lang.NullPointerException：尝试在空对象引用上调用虚方法'void android.widget.ImageView.setImageBitmap（android.graphics.Bitmap）' 在com.example.s.myapplication.MainActivity.onActivityResult（MainActivity.java:46）在android.app.Activity.dispatchActivityResult（Activity.java:6139）在android.app.ActivityThread.deliverResults（ActivityThread.java:3535）在android.app.ActivityThread.handleSendResult（ActivityThread.java:3582）在android.app.ActivityThread.access $ 1300（ActivityThread.java:144）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1327）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5221） at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:899）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:694）一个

这是我的主要活动。该应用程序的目的是：

拍张照片
将照片保存在tmp位置
将照片加载到imageview

package com.example.s.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;

import java.io.File;


public class MainActivity extends Activity {

    static final int REQUEST_IMAGE_CAPTURE = 1;
    private ImageView imageView;



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

    public void openCamera() {
        Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        File file = new File(Environment.getExternalStorageDirectory() + File.separator + "image.jpg");
        takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
    }



    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        //Check that request code matches ours:
        if (requestCode == REQUEST_IMAGE_CAPTURE) {
            //Get our saved file into a bitmap object:
            File file = new File(Environment.getExternalStorageDirectory() + File.separator + "image.jpg");
            Bitmap image = decodeSampledBitmapFromFile(file.getAbsolutePath(), 1000, 700);
            imageView.setImageBitmap(image);
        }
    }

    public boolean isExternalStorageWritable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state)) {
            return true;
        }
        return false;
    }

    public static Bitmap decodeSampledBitmapFromFile(String path, int reqWidth, int reqHeight) { 

        //First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(path, options);

        // Calculate inSampleSize, Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        options.inPreferredConfig = Bitmap.Config.RGB_565;
        int inSampleSize = 1;

        if (height > reqHeight) {
            inSampleSize = Math.round((float) height / (float) reqHeight);
        }
        int expectedWidth = width / inSampleSize;

        if (expectedWidth > reqWidth) {
            //if(Math.round((float)width / (float)reqWidth) > inSampleSize) // If bigger SampSize..
            inSampleSize = Math.round((float) width / (float) reqWidth);
        }

        options.inSampleSize = inSampleSize;

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;

        return BitmapFactory.decodeFile(path, options);
    }

    public void capture_btn(View v) {
        Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        File file = new File(Environment.getExternalStorageDirectory() + File.separator + "image.jpg");
        takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
    }
}

Answer 1

imageView = (ImageView)findViewById(R.id.imageView2);

Answer 2

这对我有用：

我写错了我的imageView的ID。应该是imageView2

imageView = findViewById（R.id.imageView2）;

Answer 3

如果上述解决方案对您不起作用

oncreate方法再次应该是这样

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);imageView=findViewById(R.id.imageView);
setContentView(R.layout.activity_main);
imageView=findViewById(R.id.imageView);

                                             }

尝试在空对象引用上调用虚方法'void android.widget.ImageView.setImageBitmap（android.graphics.Bitmap）'

3 个答案: