java.lang.NullPointerException从错误返回空？
java.lang.NullPointerException从错误返回空？
提问于 2015-10-11 14:01:47
当我删除测试代码时，这一行出现了错误。
Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);由于出现了错误java.lang.NullPointerException，image似乎变得空了
这是我得到图像的代码
public class OkHttpHandler extends AsyncTask<Void, Void, byte[]> {
private final String IMAGE_URL = "http://bit.ly/1DU2Zka";
OkHttpClient httpClient = new OkHttpClient();
@Override
protected byte[] doInBackground(Void... params) {
Log.d("e", "dddddddddd");
Log.d("e", IMAGE_URL);
Request.Builder builder = new Request.Builder();
builder.url(IMAGE_URL);
Request request = builder.build();
try {
Response response = httpClient.newCall(request).execute();
System.out.println(response);
Log.d("e", "FFFFFF response");
return response.body().bytes();
} catch (Exception e) {
Log.d("e", "rrrrrrr");
e.printStackTrace();
Log.d("e", "rrrrrrr");
}
return null;
}
}这是正确的return null;吗
就像这样，我得到了mainactivity中的图像
public void downloadImage() {
OkHttpHandler handler = new OkHttpHandler();
byte[] image = new byte[0];
try {
image = handler.execute().get();
Log.d("e", "hhhh handler");
System.out.print(image);
if (image != null && image.length > 0){
Log.isLoggable("e",image.length);
Log.d("e", "ddddddd entered the try");
Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
imageView.setImageBitmap(bitmap);
// txtBytes.setText("Total bytes downloaded: " + image.length);
}
} catch (Exception e) {
Log.d("e", "rrrrrr error");
e.printStackTrace();
// txtBytes.setText("Hmm sorry, something went wrong!");
}
}为什么我要破例？
逻辑猫
10-11 16:55:22.724 27814-27814/com.justedhak.www.i D/e﹕ ddddddd entered the try
10-11 16:55:22.739 27814-27814/com.justedhak.www.i D/e﹕ rrrrrr error
10-11 16:55:22.739 27814-27814/com.justedhak.www.i W/System.err﹕ java.lang.NullPointerException
10-11 16:55:22.739 27814-27814/com.justedhak.www.i W/System.err﹕ at com.justedhak.www.i.MainActivity.downloadImage(MainActivity.java:82)
10-11 16:55:22.739 27814-27814/com.justedhak.www.i W/System.err﹕ at com.justedhak.www.i.MainActivity.onCreate(MainActivity.java:54)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.Activity.performCreate(Activity.java:5389)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2256)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2350)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.ActivityThread.access$800(ActivityThread.java:163)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1257)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:102)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.os.Looper.loop(Looper.java:157)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5335)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:515)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
10-11 16:55:22.744 27814-27814/com.justedhak.www.i W/System.err﹕ at dalvik.system.NativeStart.main(Native Method)回答 2
Stack Overflow用户
回答已采纳
发布于 2015-10-11 14:30:34
我猜想问题是在您的主程序中分配图像(在您进入try块之前)。你只保留了一个字节，可以吗？
然后你试着把一个图像传递给一个字节，这似乎产生了问题。也许Java只是将图片的第一个字节放到变量映像中。这就是为什么您传递if条件，但如果您试图创建一个位图，则失败。
祝好运
Stack Overflow用户
发布于 2015-10-11 14:38:56
空指针异常显示当您没有正确初始化某物时。检查OnCreate方法，您是否正确地初始化了所有内容？
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/33065868
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