我必须修复一个错误 nullpointerexception

Question

我有一个仅出现在 froyo 设备中的错误

Bitmap.createScaledBitmap() 中的空指针异常

java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:200)
at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
at java.lang.Thread.run(Thread.java:1019)
Caused by: java.lang.NullPointerException
at android.graphics.Bitmap.createScaledBitmap(Bitmap.java:344)
at com.varxstudio.beautifulwallpapersLite.Imagen.a(Unknown Source)
at com.varxstudio.beautifulwallpapersLite.g.a(Unknown Source)
at com.varxstudio.beautifulwallpapersLite.g.doInBackground(Unknown Source)
at android.os.AsyncTask$2.call(AsyncTask.java:185)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)

这里的代码有什么解决方案吗？为什么只在froyo？？？ 以前只使用 BitmapFactory.decodeStream(inputStream) 来加载图像，但我找到了一个flusedInputStream方法来做到这一点，但我仍然得到同样的错误

private class DownloadDialog extends AsyncTask<Void, Void, Void> {

    ProgressDialog myDialog = null;
    int result = 0;

    @Override
    protected void onPreExecute() {
        myDialog = ProgressDialog.show(Imagen.this, "", advert);
        myDialog.setCancelable(true);
        return;
    }

    @Override
    protected Void doInBackground(Void... params) {
        result = setWallpaper(path);

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        myDialog.dismiss();
        switch (result){
            ----
        }
        return;
    }
}

public int setWallpaper(String path) {          
    int width, height;
    Bitmap dbm, bm;         
    bm = null;
    dbm = null; 
    InputStream is = null;

    WallpaperManager wpm = WallpaperManager.getInstance(this);
    dis = getWindowManager().getDefaultDisplay();           

    if((wpm != null) && (dis != null)){ 
        height = dis.getHeight();
        width = (int) (height * 1.33);              

        try {           
            URLConnection conn = new URL(path).openConnection();                
            conn.connect();             
            is = conn.getInputStream();             

            if (is != null) {                   
                bm = BitmapFactory.decodeStream(new FlushedInputStream(is));                    
                dbm = Bitmap.createScaledBitmap(bm, width, height, false);
                wpm.setBitmap(dbm);                 
            }else {
                return 2;
            }

        } catch (MalformedURLException e) {                 
            e.printStackTrace();                
        } catch (IOException e) {               
            e.printStackTrace();                
        } finally {             
            if (is != null) {
                try {
                    is.close();
                }
                catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }           
        if(bm != null){
            bm.recycle();
        }
        if(dbm != null){
            dbm.recycle();  
        }           
    }else {
        return 1;
    }
    return 0;
}

static class FlushedInputStream extends FilterInputStream {
    public FlushedInputStream(InputStream inputStream) {
        super(inputStream);
    }

    @Override
    public long skip(long n) throws IOException {
        long totalBytesSkipped = 0L;
        while (totalBytesSkipped < n) {
            long bytesSkipped = in.skip(n - totalBytesSkipped);
            if (bytesSkipped == 0L) {
                int b = read();
                if (b < 0) {
                    break;  // we reached EOF
                } else {
                    bytesSkipped = 1; // we read one byte
                }
            }
            totalBytesSkipped += bytesSkipped;
        }
        return totalBytesSkipped;
    }
}

Answer 1

你有 NullPointerException 因为 BitmapFactory.decodeStream(new FlushedInputStream(is)); 返回 null，BitmapFactory.decodeStream(stream) 返回 null 的原因是因为图像不好.. 从某种意义上说，坏图像确保您返回的是 Android 支持的位图格式（例如 Android doesn't support tiff）。第二个原因是因为图像分辨率，如果图像分辨率太高解码失败..所以确保你有小图像。

这是我在 SO 中发布的关于同一问题的问题..Bitmap failed to create using BitmapFactory.decodeArray

我之前也遇到过同样的问题，但是我通过使用Android开发者网站Displaying Bitmaps Efficiently提供的教程解决了这个问题