Question

我正试图用手机的相机拍下这段代码：

MainActivity：

package com.m.textdetection;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.icu.text.SimpleDateFormat;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import java.io.File;
import java.io.IOException;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private MyTessOCR mTessOCR = new MyTessOCR(MainActivity.this);

    private Button takePictureButton;
    private ImageView imageView;



    int TAKE_PHOTO_CODE = 0;
    public static int count = 0;


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

        final String dir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES) + "/picFolder/";
        File newdir = new File(dir);
        newdir.mkdirs();

        Button capture = (Button) findViewById(R.id.btnCapture);
        capture.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                // Here, the counter will be incremented each time, and the
                // picture taken by camera will be stored as 1.jpg,2.jpg
                // and likewise.
                count++;
                String file = dir+count+".jpg";
                File newfile = new File(file);
                try {
                    newfile.createNewFile();
                }
                catch (IOException e)
                {
                }

           //     Uri outputFileUri = Uri.fromFile(newfile);
                Uri outputFileUri = FileProvider.getUriForFile(MainActivity.this, BuildConfig.APPLICATION_ID, newfile);

                Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);

                startActivityForResult(cameraIntent, TAKE_PHOTO_CODE);
            }
        });


    }

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

        if (requestCode == TAKE_PHOTO_CODE && resultCode == RESULT_OK) {
            Log.d("CameraDemo", "Pic saved");
        }
    }


    private void doOCR()
    {
     //   String temp = mTessOCR.getOCRResult(bitmap);

    }

}

清单：

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.m.textdetection">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <provider
            android:name="android.support.v4.content.FileProvider"
            android:authorities="${applicationId}.my.package.name.provider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/provider_paths"/>
        </provider>

    </application>

</manifest>

我还将其添加到build.gradle(app)：

编译'com.android.support:support-v4:27.0.2'

但我收到此错误消息：

java.lang.NullPointerException：尝试调用虚方法 “android.content.res.XmlResourceParser android.content.pm.ProviderInfo.loadXmlMetaData（android.content.pm.PackageManager， “空对象引用
上的java.lang.String）”

在这行代码中：

        Uri outputFileUri = FileProvider.getUriForFile(MainActivity.this, BuildConfig.APPLICATION_ID, newfile);

问题是什么？我该如何解决？有没有更简单，更简单的方法从相机拍摄照片并将其保存在存储空间？

编辑：我看到了这个链接地址What is a NullPointerException, and how do I fix it?，但这是一般性主题，我无法理解为什么会收到此错误消息？

我再次检查了这行代码Uri outputFileUri = FileProvider.getUriForFile(MainActivity.this, BuildConfig.APPLICATION_ID, newfile);并且MainActivity存在，第二个参数是预先定义的，最后一个参数是存在的，它创建了文件1.jpg，但它的内容为空！

Answer 1

enter image description here

enter code here  if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N){
        mPhotoFile = StorageUtil.genSystemPhotoFile();
        if (!mPhotoFile.getParentFile().exists()) {
            mPhotoFile.getParentFile().mkdirs();
        }

        Uri imageUri = FileProvider.getUriForFile(this,
                "cn.timeface.party.fileProvider", mPhotoFile);//通过FileProvider创建一个content类型的Uri
        Intent intent = new Intent();
        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION); //添加这一句表示对目标应用临时授权该Uri所代表的文件
        intent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);//设置Action为拍照
        intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);//将拍取的照片保存到指定URI
        startActivityForResult(intent,PHOTO_SELECT_CAMERA_REQUEST_CODE);
    }

按图示方式修改即可

错误：尝试调用虚拟方法'android.content.res.XmlResourceParser android.content.pm.ProviderInfo.loadXmlMetaData

1 个答案: