嗨在我的应用程序中，我通过传递URL并显示包含内容的图像来解析数据。
之后我添加了一个按钮如果我点击按钮我想下载内容和图像并将其保存到sdcard.Now，如果我按下载按钮它显示不幸的错误。
现在我想如果我按下载按钮我想下载包含图像的完整内容并保存到SD卡。
任何人都可以帮助我。
notify_image类
public class notify_image extends Activity {
Activity av=notify_image.this;
ImageView imageView;
View content;
Button download;
Activity activity;
Button btnShowProgress;
private ProgressDialog pDialog;
ImageView my_image;
public static final int progress_bar_type = 0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.notify_image);
imageView = (ImageView) findViewById(R.id.iv_imageview);
btnShowProgress = (Button) findViewById(R.id.button1);
my_image = (ImageView) findViewById(R.id.my_image);
// download = (Button) findViewById(R.id.button1);
Intent in = getIntent();
String title = in.getStringExtra("TAG_TITLE");
String url = in.getStringExtra("TAG_URL");
String name = in.getStringExtra("TAG_NAME");
String place = in.getStringExtra("TAG_PLACE");
String date = in.getStringExtra("TAG_DATE");
final String URL =url;
TextView stitle = (TextView) findViewById(R.id.tv_title);
TextView sname = (TextView) findViewById(R.id.tv_name);
TextView splace = (TextView) findViewById(R.id.tv_place);
TextView sdate = (TextView) findViewById(R.id.tv_date);
// displaying selected product name
stitle.setText(title);
sname.setText(name);
splace.setText(place);
sdate.setText(date);
// Create an object for subclass of AsyncTask
GetXMLTask task = new GetXMLTask();
// Execute the task
task.execute(new String[] { URL });
btnShowProgress.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// starting new Async Task
new DownloadFileFromURL().execute(URL);
}
});
//download();
}
class DownloadFileFromURL extends AsyncTask<String, String, String> {
/**
* Before starting background thread
* Show Progress Bar Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
showDialog(progress_bar_type);
}
protected void onProgressUpdate(String... progress) {
// setting progress percentage
pDialog.setProgress(Integer.parseInt(progress[0]));
}
protected void onPostExecute(String file_url) {
// dismiss the dialog after the file was downloaded
dismissDialog(progress_bar_type);
// Displaying downloaded image into image view
// Reading image path from sdcard
String imagePath = Environment.getExternalStorageDirectory().toString() + "/downloadedfile.jpg";
// setting downloaded into image view
my_image.setImageDrawable(Drawable.createFromPath(imagePath));
}
/**
* Downloading file in background thread
* */
@Override
protected String doInBackground(String... f_url) {
int count;
try {
URL url = new URL(f_url[0]);
URLConnection conection = url.openConnection();
conection.connect();
// getting file length
int lenghtOfFile = conection.getContentLength();
// input stream to read file - with 8k buffer
InputStream input = new BufferedInputStream(url.openStream(), 8192);
// Output stream to write file
OutputStream output = new FileOutputStream("/sdcard/downloadedfile.jpg");
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
// After this onProgressUpdate will be called
publishProgress(""+(int)((total*100)/lenghtOfFile));
// writing data to file
output.write(data, 0, count);
}
// flushing output
output.flush();
// closing streams
output.close();
input.close();
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return null;
}
}
//image url convert to bitmap
private class GetXMLTask extends AsyncTask<String, Void, Bitmap> {
@Override
protected Bitmap doInBackground(String... urls) {
Bitmap map = null;
for (String url : urls) {
map = downloadImage(url);
}
return map;
}
// Sets the Bitmap returned by doInBackground
@Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
// Creates Bitmap from InputStream and returns it
private Bitmap downloadImage(String url) {
Bitmap bitmap = null;
InputStream stream = null;
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inSampleSize = 1;
try {
stream = getHttpConnection(url);
bitmap = BitmapFactory.
decodeStream(stream, null, bmOptions);
stream.close();
} catch (IOException e1) {
e1.printStackTrace();
}
return bitmap;
}
// Makes HttpURLConnection and returns InputStream
private InputStream getHttpConnection(String urlString)
throws IOException {
InputStream stream = null;
URL url = new URL(urlString);
URLConnection connection = url.openConnection();
try {
HttpURLConnection httpConnection = (HttpURLConnection) connection;
httpConnection.setRequestMethod("GET");
httpConnection.connect();
if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
stream = httpConnection.getInputStream();
}
} catch (Exception ex) {
ex.printStackTrace();
}
return stream;
}
}
}
Logcat错误
07-15 14:27:26.457: E/AndroidRuntime(14670): FATAL EXCEPTION: main
07-15 14:27:26.457: E/AndroidRuntime(14670): java.lang.NullPointerException
07-15 14:27:26.457: E/AndroidRuntime(14670): at com.politicalmileage.vel.notify_image$DownloadFileFromURL.onProgressUpdate(notify_image.java:122)
07-15 14:27:26.457: E/AndroidRuntime(14670): at com.politicalmileage.vel.notify_image$DownloadFileFromURL.onProgressUpdate(notify_image.java:1)
07-15 14:27:26.457: E/AndroidRuntime(14670): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:647)
07-15 14:27:26.457: E/AndroidRuntime(14670): at android.os.Handler.dispatchMessage(Handler.java:107)
07-15 14:27:26.457: E/AndroidRuntime(14670): at android.os.Looper.loop(Looper.java:194)
07-15 14:27:26.457: E/AndroidRuntime(14670): at android.app.ActivityThread.main(ActivityThread.java:5371)
07-15 14:27:26.457: E/AndroidRuntime(14670): at java.lang.reflect.Method.invokeNative(Native Method)
07-15 14:27:26.457: E/AndroidRuntime(14670): at java.lang.reflect.Method.invoke(Method.java:525)
07-15 14:27:26.457: E/AndroidRuntime(14670): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
07-15 14:27:26.457: E/AndroidRuntime(14670): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
07-15 14:27:26.457: E/AndroidRuntime(14670): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
您致电pDialog.setProgress(Integer.parseInt(progress[0]));但pDialog未设置且等于null。您必须在LOG CAT中为错误设置变量。
pDialog = new ProgressDialog(this);