尝试保存图像时出现Android运行时错误

编程问答 2022-06-08

问题描述

我的android应用程序的Logcat显示错误：

2020-10-15 11:08:44.135 26149-26149/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.documentscanner,PID: 26149
    java.lang.RuntimeException: Failure delivering result ResultInfo{who=null,request=99,result=-1,data=Intent { (has extras) }} to activity {com.example.documentscanner/com.example.documentscanner.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference
        at android.app.ActivityThread.deliverResults(ActivityThread.java:5183)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5224)
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:151)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:111)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2213)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:238)
        at android.app.ActivityThread.main(ActivityThread.java:7853)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:984)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference
        at com.example.documentscanner.HomeActivity.onActivityResult(HomeActivity.java:101)
        at android.app.Activity.dispatchActivityResult(Activity.java:8309)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:5176)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5224) 
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:151) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:111) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2213) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:238) 
        at android.app.ActivityThread.main(ActivityThread.java:7853) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:984) 

package com.example.documentscanner;

import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.widget.ImageView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.scanlibrary.ScanActivity;
import com.scanlibrary.ScanConstants;

import java.io.IOException;

public class HomeActivity extends AppCompatActivity {

    private static final int PERMISSION_CODE = 1000;
    ImageView scannedImageView = null;

    int REQUEST_CODE = 99;

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

    }


    public void checkCamera(View v) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(Manifest.permission.CAMERA) ==
                    PackageManager.PERMISSION_DENIED || checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) ==
                    PackageManager.PERMISSION_DENIED) {
                String[] permission = {Manifest.permission.CAMERA,Manifest.permission.WRITE_EXTERNAL_STORAGE};
                requestPermissions(permission,PERMISSION_CODE);
            } else {
                openCamera();
            }

        } else {
            openCamera();

        }

    }

    public void checkGallery(View v){
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if(checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) ==
                    PackageManager.PERMISSION_DENIED || checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) ==
                    PackageManager.PERMISSION_DENIED){
               String[] permission = {Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE};
               requestPermissions(permission,PERMISSION_CODE);
            } else {
                openGallery();
            }
        } else
        {
            openGallery();
        }
    }


    public void openCamera(){

        int preference = ScanConstants.OPEN_CAMERA;
        Intent intent = new Intent(this,ScanActivity.class);
        intent.putExtra(ScanConstants.OPEN_INTENT_PREFERENCE,preference);
        startActivityForResult(intent,REQUEST_CODE);

    }

    public void openGallery(){

        int preference = ScanConstants.OPEN_MEDIA;
        Intent intent = new Intent(this,REQUEST_CODE);

    }

    @Override
    protected void onActivityResult(int requestCode,int resultCode,@Nullable Intent data) {
        super.onActivityResult(requestCode,resultCode,data);

        if (requestCode == REQUEST_CODE && resultCode == Activity.RESULT_OK) {
            Uri uri = data.getExtras().getParcelable(ScanConstants.SCANNED_RESULT);
            Bitmap bitmap = null;
            try {
                bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(),uri);
                getContentResolver().delete(uri,null,null);
                scannedImageView.setImageBitmap(bitmap);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

解决方法

scannedImageView为空，您必须先绑定视图，然后才能使用它。替换为您的ImageView在XML中具有的ID。查看OnCreate()方法：

package com.example.documentscanner;

import android.Manifest;
import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.widget.ImageView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.scanlibrary.ScanActivity;
import com.scanlibrary.ScanConstants;

import java.io.IOException;

public class HomeActivity extends AppCompatActivity {

    private static final int PERMISSION_CODE = 1000;
    ImageView scannedImageView = null;

    int REQUEST_CODE = 99;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
    
        //REPLACE WITH YOUR ID
        scannedImageView = findViewById(R.id.YourId);
    }


    public void checkCamera(View v) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(Manifest.permission.CAMERA) ==
                    PackageManager.PERMISSION_DENIED || checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) ==
                    PackageManager.PERMISSION_DENIED) {
                String[] permission = {Manifest.permission.CAMERA,Manifest.permission.WRITE_EXTERNAL_STORAGE};
                requestPermissions(permission,PERMISSION_CODE);
            } else {
                openCamera();
            }

        } else {
            openCamera();

        }

    }

    public void checkGallery(View v){
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if(checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) ==
                    PackageManager.PERMISSION_DENIED || checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE) ==
                    PackageManager.PERMISSION_DENIED){
               String[] permission = {Manifest.permission.READ_EXTERNAL_STORAGE,Manifest.permission.WRITE_EXTERNAL_STORAGE};
               requestPermissions(permission,PERMISSION_CODE);
            } else {
                openGallery();
            }
        } else
        {
            openGallery();
        }
    }


    public void openCamera(){

        int preference = ScanConstants.OPEN_CAMERA;
        Intent intent = new Intent(this,ScanActivity.class);
        intent.putExtra(ScanConstants.OPEN_INTENT_PREFERENCE,preference);
        startActivityForResult(intent,REQUEST_CODE);

    }

    public void openGallery(){

        int preference = ScanConstants.OPEN_MEDIA;
        Intent intent = new Intent(this,REQUEST_CODE);

    }

    @Override
    protected void onActivityResult(int requestCode,int resultCode,@Nullable Intent data) {
        super.onActivityResult(requestCode,resultCode,data);

        if (requestCode == REQUEST_CODE && resultCode == Activity.RESULT_OK) {
            Uri uri = data.getExtras().getParcelable(ScanConstants.SCANNED_RESULT);
            Bitmap bitmap = null;
            try {
                bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(),uri);
                getContentResolver().delete(uri,null,null);
                scannedImageView.setImageBitmap(bitmap);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
androidandroidimage-scannerjavajavalogcatruntime-error

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