位图压缩：空点异常错误

Question

尝试压缩位图时出现空指针异常，因此我可以将其发送到 ByteArrayOutputStream 以获取字节数组。日志错误如下所示。

java.lang.RuntimeException: An error occurred while executing doInBackground()
                                                                             at android.os.AsyncTask$3.done(AsyncTask.java:309)
                                                                             at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
                                                                             at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
                                                                             at java.util.concurrent.FutureTask.run(FutureTask.java:242)
                                                                             at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
                                                                             at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
                                                                             at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
                                                                             at java.lang.Thread.run(Thread.java:818)
                                                                          Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.graphics.Bitmap.compress(android.graphics.Bitmap$CompressFormat, int, java.io.OutputStream)' on a null object reference
                                                                             at worldnp.zpmobi.mobi.test.MainActivity$Encode_image.doInBackground(MainActivity.java:102)
                                                                             at worldnp.zpmobi.mobi.test.MainActivity$Encode_image.doInBackground(MainActivity.java:94)
                                                                             at android.os.AsyncTask$2.call(AsyncTask.java:295)

java代码：

protected Void doInBackground(Void... voids) {

            bitmap = BitmapFactory.decodeFile(file_uri.getPath());
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
            bitmap.recycle();

            byte[] array = stream.toByteArray();
            encoded_string = Base64.encodeToString(array, 0);
            return null;
        }

当位图应该被压缩时，应用程序就会崩溃。我的代码哪里做错了？

Answer 1

protected Void doInBackground(Void... voids) {

        Bitmap bitmap = BitmapFactory.decodeFile(file_uri.getPath());
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
        bitmap.recycle();

        byte[] array = stream.toByteArray();
        encoded_string = Base64.encodeToString(array, 0);
        return null;
    }

你在初始化变量bitmap时没有给它一个类型。