在我的一个项目中，我正在从动态网址加载图片。现在我需要显示所有图像加载的加载对话框。我正在使用Async任务加载图像。 我是android的新手。请任何人给我一点帮助
我的代码看起来像。
TableLayout table = (TableLayout)findViewById(R.id.tableLayout_1);
for(Integer i=0;i<2;i++){
TableRow rowP = new TableRow(this);
rowP.setBackgroundColor(Color.parseColor("#FFF000"));
ImageView image = new ImageView(this);
String ed="http://www.domain.com/image.jpg";
image.setTag(ed);
DownloadImagesTask td=new DownloadImagesTask();
td.execute(image);
rowP.addView(image);
table.addView(rowP);
}
}
private class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
@Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
@Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
private Bitmap download_Image(String url) {
Bitmap bmp =null;
try{
URL ulrn = new URL(url);
HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
InputStream is = con.getInputStream();
bmp = BitmapFactory.decodeStream(is);
if (null != bmp)
return bmp;
}catch(Exception e){}
return bmp;
}
}
提前致谢
修改
private class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
ProgressDialog dialog;
Context context;
public DownloadImagesTask(Context context) {
this.context = context;
}
@Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
@Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
if (dialog != null)
dialog.dismiss();
}
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog = ProgressDialog.show(context, "Title","Message");
}
private Bitmap download_Image(String url) {
Bitmap bmp =null;
try{
URL ulrn = new URL(url);
HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
InputStream is = con.getInputStream();
bmp = BitmapFactory.decodeStream(is);
if (null != bmp)
return bmp;
}catch(Exception e){}
return bmp;
}
}
答案 0 :(得分：4)
在DownloadImageTask。
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog = ProgressDialog.show(context, "Title",
"Message");
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
if (dialog != null)
dialog.dismiss();
//rest of the code
}
并在ProgressDialog dialog中声明DownloadImageTask。
要传递Context，您需要为此创建一个构造函数。
private class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
ProgressDialog dialog;
Context context;
public DownloadImagesTask(Context context) {
this.context = context;
}
//... rest of code ....
}
答案 1 :(得分：4)
如果你想保持它简单/清晰/快速和漂亮，你不应该自己下载，特别是如果你是Android新手。
只需使用开源库：
最简单的是 http://square.github.io/picasso/
另一个更复杂的问题：https://github.com/nostra13/Android-Universal-Image-Loader
答案 2 :(得分：2)
如果要在进度条上显示进度，可以使用此代码。它就像一个魅力。
这里dwBar是进度条。 imView是你想要显示图片的imageView。
private class DownloadImageTask extends AsyncTask<String, String, Bitmap> {
@Override
protected void onPreExecute() {
super.onPreExecute();
dwBar.setVisibility(View.VISIBLE);
}
@Override
protected Bitmap doInBackground(String... params) {
Bitmap bitmap = null;
try {
int increment;
byte[] data;
InputStream in = null;
int response;
URL url = new URL(params[0]);
URLConnection conn = url.openConnection();
if (!(conn instanceof HttpURLConnection))
throw new IOException("Not an HTTP connection");
try {
HttpURLConnection httpConn = (HttpURLConnection) conn;
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
response = httpConn.getResponseCode();
if (response == HttpURLConnection.HTTP_OK) {
in = httpConn.getInputStream();
}
int length = httpConn.getContentLength();
data = new byte[length];
increment = length / 100;
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
int count = -1;
int progress = 0;
while ((count = in.read(data, 0, increment)) != -1) {
progress += count;
publishProgress("" + (int) ((progress * 100) / length));
outStream.write(data, 0, count);
}
bitmap = BitmapFactory.decodeByteArray(
outStream.toByteArray(), 0, data.length);
in.close();
outStream.close();
} catch (Exception ex) {
Log.d("Networking", ex.getLocalizedMessage());
throw new IOException("Error connecting");
}
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return bitmap;
}
protected void onProgressUpdate(String... progress) {
dwBar.setProgress(Integer.parseInt(progress[0]));
}
protected void onPostExecute(Bitmap bm) {
dwBar.setVisibility(View.GONE);
if (bm != null) {
imView.setImageBitmap(bm);
}
}
}
答案 3 :(得分：0)
以下是在屏幕上下载和显示图像的完整domanstration of actvity。
这是Activity的xml文件。
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<!-- Download Button -->
<Button android:id="@+id/btnProgressBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Download File with Progress Bar"
android:layout_marginTop="50dip"/>
<!-- Image view to show image after downloading -->
<ImageView android:id="@+id/my_image"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
这是活动代码。
import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
public class AndroidDownloadFileByProgressBarActivity extends Activity {
// button to show progress dialog
Button btnShowProgress;
// Progress Dialog
private ProgressDialog pDialog;
ImageView my_image;
// Progress dialog type (0 - for Horizontal progress bar)
public static final int progress_bar_type = 0;
// File url to download
private static String file_url = "http://api.androidhive.info/progressdialog/hive.jpg";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_android_download_file_by_progress_bar);
// show progress bar button
btnShowProgress = (Button) findViewById(R.id.btnProgressBar);
// Image view to show image after downloading
my_image = (ImageView) findViewById(R.id.my_image);
/**
* Show Progress bar click event
* */
btnShowProgress.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// starting new Async Task
new DownloadFileFromURL().execute(file_url);
}
});
}
/**
* Showing Dialog
* */
@SuppressWarnings("deprecation")
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case progress_bar_type: // we set this to 0
pDialog = new ProgressDialog(this);
pDialog.setMessage("Downloading file. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setMax(100);
pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pDialog.setButton("Cancel", (DialogInterface.OnClickListener) null);
pDialog.setCancelable(true);
pDialog.show();
return pDialog;
default:
return null;
}
}
/**
* Background Async Task to download file
* */
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);
}
/**
* 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();
// this will be useful so that you can show a tipical 0-100% progress
// bar
int lenghtOfFile = conection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream(), 8192);
// Output stream
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;
}
/**
* Updating progress bar
* */
protected void onProgressUpdate(String... progress) {
// setting progress percentage
pDialog.setProgress(Integer.parseInt(progress[0]));
}
/**
* After completing background task Dismiss the progress dialog
* **/
@Override
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));
}
}
}
只需使用以下xml文件添加此活动。