android.content.ContentResolver.openInputStream 将图像发送到 PHP 服务器时出现 NullPointerException

Question

我根据教程修改Android Upload Image to Server using Volley Tutorial

在本教程中，当用户select一张图片时，脚本直接上传到服务器。所以我修改了当用户 select 图像时，图像首先显示在 imageview 上，然后，当用户单击 "sendtoserver" 按钮时，该图像将与其他 EditText 一起发送到服务器。

首先，我完成了选择图像按钮，我选择的图像显示在 imageview 上。

其次，当我点击 "sendtoserver" 按钮时，我得到关于 getContentResolver() 的错误，这里是我的 MainActivity 代码

package com.example.celmira.uploadgambar;

import android.Manifest;
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.provider.Settings;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;

import com.android.volley.AuthFailureError;
import com.android.volley.NetworkResponse;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.Volley;
import com.squareup.picasso.Picasso;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;


public class MainActivity extends AppCompatActivity {

//ImageView to display image selected
ImageView imageView;
//edittext for getting the tags input
EditText editTextTags;

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

    //initializing views
    imageView = (ImageView) findViewById(R.id.imageView);
    editTextTags = (EditText) findViewById(R.id.editTextTags);

    //mengecek permission, jika blm diijinkan, maka buka setting atau keluar apps
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && ContextCompat.checkSelfPermission(this,
            Manifest.permission.READ_EXTERNAL_STORAGE)
            != PackageManager.PERMISSION_GRANTED) {
        Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS, Uri.parse("package:" + getPackageName()));
        finish();
        startActivity(intent);
        return;
    }


    //get image from gallery when clicked
    findViewById(R.id.buttonUploadImage).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            //if the tags edittext is empty
            //we will throw input error
            if (editTextTags.getText().toString().trim().isEmpty()) {
                editTextTags.setError("Enter tags first");
                editTextTags.requestFocus();
                return;
            }

            //if everything is ok we will open image chooser
            Intent i = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
            startActivityForResult(i, 100);
        }
    });


    // SENDING IMAGE AND TAG TO SERVER WHEN BUTTON sendtoserver clicked
    findViewById(R.id.sendtoserver).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Uri imageUri = getIntent().getData();

            try {
                //getting bitmap object from uri
                Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), imageUri);
                Log.d("eek",bitmap.toString());

                //function to send to server
                uploadBitmap(bitmap);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 100 && resultCode == RESULT_OK && data != null) {

        //getting the image Uri
        Uri imageUri = data.getData();
        try {
            //getting bitmap object from uri
            Bitmap bitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageUri);
            //displaying selected image to imageview
            Picasso.get().load(imageUri).into(imageView);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

/*
* The method is taking Bitmap as an argument
* then it will return the byte[] array for the given bitmap
* and we will send this array to the server
* here we are using PNG Compression with 80% quality
* you can give quality between 0 to 100
* 0 means worse quality
* 100 means best quality
* */
public byte[] getFileDataFromDrawable(Bitmap bitmap) {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.PNG, 80, byteArrayOutputStream);
    return byteArrayOutputStream.toByteArray();
}

private void uploadBitmap(final Bitmap bitmap) {

    //getting the tag from the edittext
    final String tags = editTextTags.getText().toString().trim();

    //our custom volley request
    VolleyMultipartRequest volleyMultipartRequest = new VolleyMultipartRequest(Request.Method.POST, "http://192.168.166.2/MyApi/Api.php?apicall=uploadpic",
            new Response.Listener<NetworkResponse>() {
                @Override
                public void onResponse(NetworkResponse response) {
                    try {
                        JSONObject obj = new JSONObject(new String(response.data));
                        Toast.makeText(getApplicationContext(), obj.getString("message"), Toast.LENGTH_SHORT).show();
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_SHORT).show();
                }
            }) {

        /*
        * If you want to add more parameters with the image
        * you can do it here
        * here we have only one parameter with the image
        * which is tags
        * */
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> params = new HashMap<>();
            params.put("tags", tags);
            return params;
        }

        /*
        * Here we are passing image by renaming it with a unique name
        * */
        @Override
        protected Map<String, DataPart> getByteData() {
            Map<String, DataPart> params = new HashMap<>();
            long imagename = System.currentTimeMillis();
            params.put("pic", new DataPart(imagename + ".png", getFileDataFromDrawable(bitmap)));
            return params;
        }
    };

    //adding the request to volley
    Volley.newRequestQueue(this).add(volleyMultipartRequest);
}
}

这里是导致错误的脚本

 Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), imageUri);

这就是错误信息

FATAL EXCEPTION: main
              java.lang.NullPointerException
                  at android.content.ContentResolver.openInputStream(ContentResolver.java:481)
                  at android.provider.MediaStore$Images$Media.getBitmap(MediaStore.java:792)
                  at com.example.celmira.uploadgambar.MainActivity.onClick(MainActivity.java:94)

如何获取我可以传递给 MediaStore.Images.Media.getBitmap()

的 getContentResolver()

Answer 1

在 select 之后上传 iamge:

将uploadBitmap(bitmap);移动到onActivityResult()

点击按钮后上传：

首先创建全局图像url

private Uri imageUri;

在你的代码上面像

一样填写 onActivityResult

imageUri = data.getData();

并在调用按钮时发送

findViewById(R.id.sendtoserver).setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        //THIS LINE REMOVED
        //Uri imageUri = getIntent().getData();

        try {
            //getting bitmap object from uri
            Bitmap bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), imageUri);
            Log.d("eek",bitmap.toString());

            //function to send to server
            uploadBitmap(bitmap);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
});

android.content.ContentResolver.openInputStream 将图像发送到 PHP 服务器时出现 NullPointerException

NullPointer Exception at android.content.ContentResolver.openInputStream When Send Image To PHP Server

android

android-image

android-volley