嗨我ProgressDailog有一个问题。我无法在我的代码中正确设置它。在我的代码中，我通过JSON数组获取图像的URL，然后下载图像，然后将它们显示在GridView中，然后点击在下一个活动中显示所选图像。这一切都很完美，但问题是因为我是在我的代码中使用AsyncTask进入后台并获取JSON，下载图像。我希望显示ProgressBar直到后台进程完成并在所有图像下载后初始化GridView ...
以下是我的代码..
public class AndroidGridLayoutActivity extends Activity {
public static ImageAdapter img;
public static String[] imageurls;
public static GridView gridView;
public static Bitmap bm[]=new Bitmap[4];
private ProgressDialog pDialog;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.grid_layout);
// Showing progress dialog
pDialog = new ProgressDialog(this);
pDialog.setMax(5);
pDialog.setMessage("Loading...");
pDialog.setCancelable(true);
pDialog.show();
new GetImageUrls().execute();
Thread thread = new Thread()
{
@Override
public void run() {
int count=0;
while(count<3) {
try {
sleep(1000);
count++;
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
if(pDialog != null && pDialog.isShowing()){
pDialog.dismiss();
}
new GetImageUrls().execute();
}
};
thread.start();
gridView = (GridView) findViewById(R.id.grid_view);
// Instance of ImageAdapter Class
img = new ImageAdapter(AndroidGridLayoutActivity.this,bm);
gridView.setAdapter(img);
/**
* On Click event for Single Gridview Item
* */
gridView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View v,
int position, long id) {
// Sending image id to FullScreenActivity
Intent i = new Intent(getApplicationContext(), FullImageActivity.class);
// passing array index
i.putExtra("id", position);
startActivity(i);
}
});
}
public class GetImageUrls extends AsyncTask<Void, Void, Void>
{
Context context = getBaseContext();
private static final String url= "http://xxx.xxx.x.xxx/demo/test.json";
private static final String MAIN = "mainCategory";
private static final String SUB = "mcatimage";
JSONArray loginjsonarray=null;
protected Void doInBackground(Void... arg) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonstr = sh.makeServiceCall(url, ServiceHandler.POST, null);
if(jsonstr!=null)
{
try {
JSONObject jsonObj =new JSONObject(jsonstr);
loginjsonarray=jsonObj.getJSONArray(MAIN);
imageurls=new String[loginjsonarray.length()];
for(int i=0;i<loginjsonarray.length();i++)
{
JSONObject l=loginjsonarray.getJSONObject(i);
imageurls[i]=l.getString(SUB);
}
for(int i=0;i<imageurls.length;i++)
{
bm[i]=DownloadImage(imageurls[i]);
}
} catch (JSONException e) {
e.printStackTrace();
}
}else{
Toast.makeText(context,"Check your Internet Connection",Toast.LENGTH_SHORT).show();
}
return null;
}
public Bitmap DownloadImage(String STRURL) {
Bitmap bitmap = null;
InputStream in = null;
try {
int response = -1;
URL url = new URL(STRURL);
Log.d("DownloadImage: ", url.toString());
URLConnection conn = url.openConnection();
if (!(conn instanceof HttpURLConnection))
throw new IOException("Not an HTTP connection");
try{
HttpURLConnection httpConn = (HttpURLConnection) conn;
httpConn.setAllowUserInteraction(false);
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
response = httpConn.getResponseCode();
Log.d("DownloadImage response: ", Integer.toString(response));
if (response == HttpURLConnection.HTTP_OK) {
in = httpConn.getInputStream();
Log.d("DownloadImage: ", in.toString());
}
} catch (Exception ex) {
throw new IOException("Error connecting");
}
bitmap = BitmapFactory.decodeStream(in);
Log.d("DownloadImage Bitmap: ", bitmap.toString());
in.close();
}catch (IOException e1) {
e1.printStackTrace();
}
return bitmap;
}
}
}
当我运行此代码时，图像会被下载但不会显示在网格视图上，当我点击任何网格时，图像会显示在下一个活动中，
ImageAdapter类：
public class ImageAdapter extends BaseAdapter {
private Context mContext;
public static Bitmap adapterbm[]=new Bitmap[4];
ImageView imageView;
public static String[] imageurls;
// Constructor
public ImageAdapter(Context c, Bitmap[] bm){
mContext = c;
adapterbm = bm;
}
public ImageAdapter(Context c) {
mContext = c;
}
@Override
public int getCount() {
return adapterbm.length;
}
@Override
public Object getItem(int position) {
return adapterbm[position];
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
imageView = new ImageView(mContext);
imageView.setImageBitmap(adapterbm[position]);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setLayoutParams(new GridView.LayoutParams(70, 70));
return imageView;
}
}
答案 0 :(得分：2)
你应该在doInBackground方法之前覆盖onPreExecute（）方法。
ProgressDialog myPd_bar;
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
myPd_bar=new ProgressDialog(AndroidGridLayoutActivity.this);
myPd_bar.setMessage("Loading....");
myPd_bar.setTitle(title);
myPd_bar.show();
super.onPreExecute();
}
然后你应该在doInBackground方法之后覆盖onPostExecute（）方法。
@Override
protected void onPostExecute(String result) {
// TODO Auto-generated method stub
myPd_bar.dismiss();
}
您可以在此link
中找到更多信息答案 1 :(得分：1)
将您的ProgressDialog放入onPreExecute，希望此代码可以帮助您：）
private ProgressDialog pdia;
@Override
protected void onPreExecute(){
super.onPreExecute();
pdia = new ProgressDialog(yourContext);
pdia.setMessage("Loading...");
pdia.show();
}
@Override
protected void onPostExecute(String result){
super.onPostExecute(result);
pdia.dismiss();
}
答案 2 :(得分：1)
Async类中还有两种方法，即onPostExecute和onPreExecute方法。在onPreExecute方法中，您可以编写以下代码
pDialog = new ProgressDialog(this);
pDialog.setMax(5);
pDialog.setMessage("Loading...");
pDialog.setCancelable(true);
pDialog.show();
onPostExecute方法使用pDialog.dismiss（）。
答案 3 :(得分：1)
使用preExcecute显示进度对话框。
ProgressDialog pDialog;
public class GetImageUrls extends AsyncTask<Void, Void, Void>{
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Activity.this);
pDialog.setMessage("Loading. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg)
{....
}
@Override
protected postExcecute()
{
pDialog.dismiss();
....//display UI
...
}
答案 4 :(得分：1)
无需撰写Thread来展示ProgressDialog。
只需要实现onPreExecute来显示对话框，onPostExecute来解除对话框。
只需更改GetImageUrls方法，如下所示：
public class GetImageUrls extends AsyncTask<Void, Void, Void>
{
Context context = getBaseContext();
private static final String url= "http://xxx.xxx.x.xxx/demo/test.json";
private static final String MAIN = "mainCategory";
private static final String SUB = "mcatimage";
JSONArray loginjsonarray=null;
@Override
protected void onPreExecute(){
super.onPreExecute();
pDialog = new ProgressDialog(this);
pDialog.setMax(5);
pDialog.setMessage("Loading...");
pDialog.setCancelable(true);
pDialog.show();
}
protected Void doInBackground(Void... arg) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonstr = sh.makeServiceCall(url, ServiceHandler.POST, null);
if(jsonstr!=null)
{
try {
JSONObject jsonObj =new JSONObject(jsonstr);
loginjsonarray=jsonObj.getJSONArray(MAIN);
imageurls=new String[loginjsonarray.length()];
for(int i=0;i<loginjsonarray.length();i++)
{
JSONObject l=loginjsonarray.getJSONObject(i);
imageurls[i]=l.getString(SUB);
}
for(int i=0;i<imageurls.length;i++)
{
bm[i]=DownloadImage(imageurls[i]);
}
} catch (JSONException e) {
e.printStackTrace();
}
}else{
Toast.makeText(context,"Check your Internet Connection",Toast.LENGTH_SHORT).show();
}
return null;
}
@Override
protected void onPostExecute(String result){
super.onPostExecute(result);
pDialog.dismiss();
}
答案 5 :(得分：0)
在
中启动对话框onPreExecute()
并解雇它
onPostExecute()
答案 6 :(得分：0)
在进行后台处理时显示进度的最简单方法！
private class GetImageUrls extends AsyncTask<String, String , String> {
ProgressDialog progressDialog;
@Override
protected void onPreExecute() {
progressDialog = ProgressDialog.show(this,null, "Loading ...", true);
progressDialog.setCancelable(true);
}
@Override
protected String doInBackground(String... arg0) {
//background process
}
protected void onProgressUpdate(String... str) {
}
protected void onPostExecute(String result) {
progressDialog.dismiss(); // once process complete it will dismiss.
}
}
答案 7 :(得分：0)
使用beelow代码：
ProgressDialog mProgressDialog;
public class GetImageUrls extends AsyncTask<Void, Void, Void>
{
Context context = getBaseContext();
private static final String url= "http://xxx.xxx.x.xxx/demo/test.json";
private static final String MAIN = "mainCategory";
private static final String SUB = "mcatimage";
JSONArray loginjsonarray=null;
@Override
protected void onPreExecute(){
super.onPreExecute();
mProgressDialog = ProgressDialog.show(AndroidGridLayoutActivity.this,
"", "Loading...");
mProgressDialog.setCancelable(false);
}
protected Void doInBackground(Void... arg) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonstr = sh.makeServiceCall(url, ServiceHandler.POST, null);
if(jsonstr!=null)
{
try {
JSONObject jsonObj =new JSONObject(jsonstr);
loginjsonarray=jsonObj.getJSONArray(MAIN);
imageurls=new String[loginjsonarray.length()];
for(int i=0;i<loginjsonarray.length();i++)
{
JSONObject l=loginjsonarray.getJSONObject(i);
imageurls[i]=l.getString(SUB);
}
for(int i=0;i<imageurls.length;i++)
{
bm[i]=DownloadImage(imageurls[i]);
}
} catch (JSONException e) {
e.printStackTrace();
}
}else{
Toast.makeText(context,"Check your Internet Connection",Toast.LENGTH_SHORT).show();
}
return null;
}
public Bitmap DownloadImage(String STRURL) {
Bitmap bitmap = null;
InputStream in = null;
try {
int response = -1;
URL url = new URL(STRURL);
Log.d("DownloadImage: ", url.toString());
URLConnection conn = url.openConnection();
if (!(conn instanceof HttpURLConnection))
throw new IOException("Not an HTTP connection");
try{
HttpURLConnection httpConn = (HttpURLConnection) conn;
httpConn.setAllowUserInteraction(false);
httpConn.setInstanceFollowRedirects(true);
httpConn.setRequestMethod("GET");
httpConn.connect();
response = httpConn.getResponseCode();
Log.d("DownloadImage response: ", Integer.toString(response));
if (response == HttpURLConnection.HTTP_OK) {
in = httpConn.getInputStream();
Log.d("DownloadImage: ", in.toString());
}
} catch (Exception ex) {
throw new IOException("Error connecting");
}
bitmap = BitmapFactory.decodeStream(in);
Log.d("DownloadImage Bitmap: ", bitmap.toString());
in.close();
}catch (IOException e1) {
e1.printStackTrace();
}
return bitmap;
}
}
@Override
protected void onPostExecute(){
if (mProgressDialog.isShowing())
mProgressDialog.dismiss();
}
}
}
答案 8 :(得分：0)
试试这个
活动类
package com.example.imagelist;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.app.Activity;
import android.app.ProgressDialog;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
public class MainActivity extends Activity {
ItemsAdapter adapter;
ListView list;
ProgressDialog myPd_bar;
static String img_url;
private String strJson1 = "";
private String url = "http://........................";
ImageView imageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int currentapiVersion = android.os.Build.VERSION.SDK_INT;
if (currentapiVersion > android.os.Build.VERSION_CODES.FROYO) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.detectAll().penaltyLog().build();
StrictMode.setThreadPolicy(policy);
}
/*
int images[] = {R.drawable.a, R.drawable.b, R.drawable.c, R.drawable.d};
*/
list = (ListView) findViewById(R.id.listView1);
accessWebService();
}
// Async Task to access the web
private class JsonReadTask extends AsyncTask<String, Void, String> {
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
myPd_bar=new ProgressDialog(MainActivity.this);
myPd_bar.setMessage("Loading....");
myPd_bar.setTitle(null);
myPd_bar.show();
super.onPreExecute();
}
@Override
protected String doInBackground(String... params) {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(params[0]);
try {
HttpResponse response = httpclient.execute(httppost);
strJson1 = inputStreamToString(
response.getEntity().getContent()).toString();
}
catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
private StringBuilder inputStreamToString(InputStream is) {
String rLine = "";
StringBuilder answer = new StringBuilder();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
try {
while ((rLine = rd.readLine()) != null) {
answer.append(rLine);
}
}
catch (IOException e) {
// e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error..." + e.toString(), Toast.LENGTH_LONG).show();
}
return answer;
}
@Override
protected void onPostExecute(String result) {
ListDrwaer();
myPd_bar.dismiss();
}
}// end async task
public void accessWebService() {
JsonReadTask task = new JsonReadTask();
// passes values for the urls string array
task.execute(new String[] { url });
}
//build hash set for list view
public void ListDrwaer(){
List<String> listImg = new ArrayList<String>();
try{
JSONObject jsonResponse = new JSONObject(strJson1);
JSONArray jsonMainNode = jsonResponse.optJSONArray("bank");
for(int i = 0; i<jsonMainNode.length();i++){
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
img_url = jsonChildNode.optString("logo");
listImg.add(img_url);
// Log.d("URL", img_url);
}
ItemsAdapter adapter = new ItemsAdapter(getApplicationContext(), listImg);
list.setAdapter(adapter);
}
catch(JSONException e){
Toast.makeText(getApplicationContext(),"Connection Error...", Toast.LENGTH_LONG).show();
}
}
}
适配器类
package com.example.imagelist;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.List;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
public class ItemsAdapter extends ArrayAdapter<Integer> {
private final Context context;
ImageView imageView;
List<String> listImg;
ItemsAdapter(Context context, List<String> listImg) {
super(context, R.layout.items_list_item);
this.context = context;
this.listImg = listImg;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return listImg.size();
}
@Override
public Integer getItem(int arg0) {
// TODO Auto-generated method stub
return arg0;
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final String text = listImg.get(position);
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = convertView;
if (null == convertView)
rowView = inflater.inflate(R.layout.items_list_item, parent, false);
imageView = (ImageView) rowView.findViewById(R.id.list_item_image);
Bitmap bitmap;
URL imageURL = null;
try {
imageURL = new URL(text);
}
catch (MalformedURLException e) {
e.printStackTrace();
}
try {
HttpURLConnection connection = (HttpURLConnection) imageURL
.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream inputStream = connection.getInputStream();
bitmap = BitmapFactory.decodeStream(inputStream);// Convert to bitmap
imageView.setImageBitmap(bitmap);
} catch (IOException e) {
e.printStackTrace();
}
return rowView ;
}
}
<强> activity_main.xml中
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="300dp"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" >
</ListView>
<强> list_item.xml
<ImageView
android:id="@+id/list_item_image"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true" />
您可以使用gridView而不是listview。
答案 9 :(得分：0)
使用onPreExecute和onPostExecute方法