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我正在编写一个应用程序，我需要放置一个图像视图，用户必须通过单击它来加载图像。单击“我要”后，用户可以选择他是打算从手机本身加载存储的图像还是从它的相机拍摄新照片。

这个问题可能是多余的，但这里揭示的类似问题/问题几乎都没有达到我想要做的事情。

Ps 我正在使用安装了 Eclipse 4.2 (JUNO) SDK 的 Android API15。

这是主要活动的片段代码，它给了我一个错误：

 package test.imgbyte.conerter;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

import android.net.Uri;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ImageView;
import android.view.View;

public class FindImgPathActivity extends Activity 
{

      private Uri mImageCaptureUri;
      static final int CAMERA_PIC_REQUEST = 1337; 

      public void onCreate(Bundle savedInstanceState)
      {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.imgfilepath);

        Button camera = (Button) findViewById(R.id.btnLoad);
        camera.setOnClickListener(new View.OnClickListener() 
        {
            public void onClick(View v) 
            {
                Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, mImageCaptureUri);
                startActivityForResult(cameraIntent, CAMERA_PIC_REQUEST);               
            }               
        });

      }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) 
    {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == CAMERA_PIC_REQUEST) 
        {  
            Bitmap thumbnail = (Bitmap) data.getExtras().get("data");
            ImageView image = (ImageView) findViewById(R.id.imgLoaded);  
            image.setImageBitmap(thumbnail);  

            String pathToImage = mImageCaptureUri.getPath();

            // pathToImage is a path you need. 

            // If image file is not in there, 
            //  you can save it yourself manually with this code:
            File file = new File(pathToImage);

            FileOutputStream fOut;
            try 
            {
                fOut = new FileOutputStream(file);
                thumbnail.compress(Bitmap.CompressFormat.JPEG, 100, fOut); // You can choose any format you want
            } 
            catch (FileNotFoundException e) 
            {
                e.printStackTrace();
            }

        }  
    }    
}

我从 LogCat 得到的错误是这样的：

11-05 19:23:11.777: E/AndroidRuntime(1206): FATAL EXCEPTION: main
11-05 19:23:11.777: E/AndroidRuntime(1206): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1337, result=-1, data=Intent { act=inline-data (has extras) }} to activity {test.imgbyte.conerter/test.imgbyte.conerter.FindImgPathActivity}: java.lang.NullPointerException
4

1 回答 1

4

啊。这个错误。我花了很长时间来解读它的含义，显然结果有一些你试图访问的空字段。在您的情况下，您尚未使用文件真正初始化的是 mImageCaptureUri 字段。启动相机意图的方法是创建一个文件，并将其 Uri 作为 EXTRA_OUTPUT 传递给意图。

File tempFile = new File("blah.jpg");
...
cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, Uri.fromFile(tempFile));
...

然后，您可以使用 file.getAbsolutePath() 方法来加载位图。

鉴于我们在这一点上，让我与您分享我上周学到的关于直接加载位图的非常重要的一点……不要这样做！我花了一个星期才明白为什么，当我明白的时候，我简直不敢相信我之前没有明白，这完全是记忆的游戏。

使用此代码有效地加载位图。（一旦你有了文件，只需在 BitmapFactory.decodeFile() 中使用 file.getAbsolutePath()）：

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            if (width > height) {
                inSampleSize = Math.round((float)height / (float)reqHeight);
            } else {
                inSampleSize = Math.round((float)width / (float)reqWidth);
            }
        }
        return inSampleSize;
    }

    public static Bitmap decodeSampledBitmapFromPath(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
        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeFile(path, options);
    }

只需将您的 file.getAbsolutePath() 作为第一个参数以及所需的宽度和高度传递给 decodeSampledBitmapFromPath 函数即可获得有效加载的位图。此代码是从Android 文档上的版本修改而来的。

编辑：

private Uri mImageCaptureUri; // This needs to be initialized.
      static final int CAMERA_PIC_REQUEST = 1337; 
private String filePath;

      public void onCreate(Bundle savedInstanceState)
      {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.imgfilepath);
// Just a temporary solution, you're supposed to load whichever directory you need here
        File mediaFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "Temp1.jpg");
filePath = mediaFile.getABsolutePath();

        Button camera = (Button) findViewById(R.id.btnLoad);
        camera.setOnClickListener(new View.OnClickListener() 
        {
            public void onClick(View v) 
            {
                Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                cameraIntent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, Uri.fromFile(mediaFile));
                startActivityForResult(cameraIntent, CAMERA_PIC_REQUEST);               
            }               
        });

      }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) 
    {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == CAMERA_PIC_REQUEST) 
        {  
            if(resultCode == RESULT_OK)
          {
int THUMBNAIL_SIZE = 64;
// Rest assured, if the result is OK, you're file is at that location
            Bitmap thumbnail = decodeSampledBitmapFromPath(filePath, THUMBNAIL_SIZE, THUMBNAIL_SIZE); // This assumes you've included the method I mentioned above for optimization
            ImageView image = (ImageView) findViewById(R.id.imgLoaded);  
            image.setImageBitmap(thumbnail);  
          }
    }    
}
于 2012-11-05T19:09:59.140 回答