我有一个gridview，当这个活动加载它显示一个白色的屏幕我检查了很多我不知道为什么它发生我正在显示图像的网格视图，这些图像来自SD卡。
我的oncreate代码如下
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
gridview = (GridView) findViewById(R.id.gridview);
gridview.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int position, long id)
{
String pdfPath = Environment.getExternalStorageDirectory().toString() + "/ICA Faculty/";
Toast.makeText(getApplicationContext(),pdfPath+((TextView) v.findViewById(R.id.hiddenPdfUrl)).getText(), Toast.LENGTH_SHORT).show();
try {
File file = new File(pdfPath+((TextView) v.findViewById(R.id.hiddenPdfUrl)).getText());
Uri path = Uri.fromFile(file);
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(path, "application/pdf");
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
} catch (Exception e) {
Toast.makeText(getApplicationContext(),"Sorry no PDF reader found.", Toast.LENGTH_SHORT).show();
}
}
});
File folder = new File(Environment.getExternalStorageDirectory() + "/ICA Faculty");
db.open();
c = db.getAllRecords();
//If data exist in local database AND "ICA Faculty" folder exist
//Getting the sd card file name from local database
if (c.moveToFirst() && folder.exists() && folder.listFiles() != null)
{
//This array list will help to create image
imgUrl = new ArrayList<String>();
pdfUrl = new ArrayList<String>();
do
{
imgUrl.add(c.getString(3));
pdfUrl.add(c.getString(2));
} while (c.moveToNext());
ImageAdapter adapter = new ImageAdapter(MainActivity.this);
gridview.setAdapter(adapter);
}
else
{
Toast.makeText(getApplicationContext(), "You need to sync to create your library.", Toast.LENGTH_LONG).show();
}
db.close();
}
private class ImageAdapter extends BaseAdapter {
private Context mContext;
private LayoutInflater mInflater;
public ImageAdapter(Context c) {
mContext = c;
mInflater = LayoutInflater.from(c);
}
public int getCount() {
return imgUrl.size();
//return c.getCount();
}
public Object getItem(int position) {
return null;
}
public long getItemId(int position) {
return 0;
}
// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
boolean result = ( position == 0 ) ? c.moveToFirst() : c.moveToNext();
if (result)
{
if (convertView == null)
{
convertView = mInflater.inflate(R.layout.grid_row_view, null);
holder = new ViewHolder();
holder.ImgThumb = (ImageView) convertView.findViewById(R.id.imgThumb);
holder.Viewcover = (ImageView) convertView.findViewById(R.id.cover);
holder.PdfUrl = (TextView) convertView.findViewById(R.id.hiddenPdfUrl);
convertView.setTag(holder);
}
else
{
holder = (ViewHolder) convertView.getTag();
}
String imagePath = Environment.getExternalStorageDirectory().toString() + "/ICA Faculty/";
holder.ImgThumb.setImageDrawable(Drawable.createFromPath(imagePath + imgUrl.get(position)));
holder.Viewcover.setImageResource(R.drawable.book_cover);
holder.PdfUrl.setText(pdfUrl.get(position));
}
return convertView;
}
private class ViewHolder {
ImageView ImgThumb;
ImageView Viewcover;
TextView PdfUrl;
}
}
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//=======================================================================================================================================
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
private ProgressDialog pDialog;
public static final int progress_bar_type = 0;
String [] stringArrayPdfUrlForLocalDB;
String [] stringArrayBookId;
//-------------------------------------------------------------------------------------------
//Method for Sync
//-------------------------------------------------------------------------------------------
public void libSyc(View v)
{
db.open();
Cursor c = db.getAllRecords();
if (c.moveToFirst())
{
db.deleteAllRecord();
}
else{}
new MyAsyncTask().execute("aa","dd");
}
//-------------------------------------------------------------------------------------------
//END Method for Sync
//-------------------------------------------------------------------------------------------
// Show Dialog
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case progress_bar_type:
pDialog = new ProgressDialog(this);
pDialog.setMessage("Making your library. \nPlease wait ...");
pDialog.setMax(100);
pDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.setCanceledOnTouchOutside(false);
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;
for(int i=0 ; i < f_url.length ; i++){
try {
URL url = new URL(f_url[i]);
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);
String fpath = getFileName(f_url[i]);
// Output stream to write file
OutputStream output = new FileOutputStream("/sdcard/"+fpath);
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);
//save File Name, Image Name, Book ID to laocal DataBase
try {
if(stringArrayPdfUrlForLocalDB.length>0)
{
for(int i=0 ; i < stringArrayPdfUrlForLocalDB.length ; i++)
{
//----------------------------------------------------------------
//Getting value from string array
//----------------------------------------------------------------
String fileName = getOnlyFileName(stringArrayPdfUrlForLocalDB[i]);
String imageName = getImageName(stringArrayPdfUrlForLocalDB[i]);
String BookId = stringArrayBookId[i];
//Toast.makeText(getApplicationContext(), "File Name: "+fileName+"\nBookId: "+BookId, Toast.LENGTH_LONG).show();
//----------------------------------------------------------------
//Inserting each File Name, Image Name, Book ID to laocal DataBase
//----------------------------------------------------------------
db.open();
long id = db.insertRecord(BookId, fileName + ".pdf", imageName);
db.close();
}
}
else
{
Toast.makeText(getApplicationContext(), "Not getting any book form server.", Toast.LENGTH_SHORT).show();
}
//populate grid view
// ImageAdapter adapter = new ImageAdapter(MainActivity.this);
// gridview.setAdapter(adapter);
// adapter.notifyDataSetChanged();
//Reloading activity
Intent intent = getIntent();
finish();
startActivity(intent);
} catch (Throwable e) {
Toast.makeText(getApplicationContext(), ""+e, Toast.LENGTH_SHORT).show();
}
}
public String getFileName(String wholePath)
{
String name=null;
int start,end;
start=wholePath.lastIndexOf('/');
end=wholePath.length(); //lastIndexOf('.');
name=wholePath.substring((start+1),end);
//Creating a folder named ICA Faculty
File directory = new File(Environment.getExternalStorageDirectory()+File.separator+"ICA Faculty");
directory.mkdirs();
name = "ICA Faculty/"+name;
System.out.println("Start:"+start+"\t\tEnd:"+end+"\t\tName:"+name);
return name;
}
public String getOnlyFileName(String wholePath)
{
String name=null;
int start,end;
start=wholePath.lastIndexOf('/');
end=wholePath.lastIndexOf('.');
name=wholePath.substring((start+1),end);
return name;
}
public String getImageName(String wholePath)
{
String name=null;
int start,end;
start=wholePath.lastIndexOf('/');
end=wholePath.length(); //lastIndexOf('.');
name=wholePath.substring((start+1),end);
//Creating a folder named ICA Faculty
File directory = new File(Environment.getExternalStorageDirectory()+File.separator+"ICA Faculty");
directory.mkdirs();
return name;
}
}
//===================================================================================================================================
//sending EmailAddress and Password to server
//===================================================================================================================================
private class MyAsyncTask extends AsyncTask<String, Integer, Double>{
String responseBody = null;
@Override
protected Double doInBackground(String... params) {
// TODO Auto-generated method stub
postData(params[0],params[1]);
return null;
}
protected void onPostExecute(Double result){
//Toast.makeText(getApplicationContext(), responseBody, Toast.LENGTH_SHORT).show();
if(responseBody!=null)
{
processResponce(responseBody);
}
else
{
Toast.makeText(getApplicationContext(), "Empty Responce.", Toast.LENGTH_LONG).show();
}
}
protected void onProgressUpdate(Integer... progress){
}
public void postData(String emailId,String passwrd) {
// Create a new HttpClient and Post Header
HttpClient httpclient = new DefaultHttpClient();
// HttpPost httppost = new
HttpPost httppost = new HttpPost("http://bumba27.byethost16.com/Ica%20Test/book_lib.xml");
try {
// Data that I am sending
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("EmailId", emailId));
nameValuePairs.add(new BasicNameValuePair("Password", passwrd));
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
// Execute HTTP Post Request
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
responseBody = EntityUtils.toString(response.getEntity());
Log.d("result", responseBody);
}
catch (Throwable t ) {
//Toast.makeText( getApplicationContext(),""+t,Toast.LENGTH_LONG).show();
Log.d("Error Time of Login",t+"");
}
}
}
//===================================================================================================================================
//END sending EmailAddress and Password to server
//===================================================================================================================================
//===================================================================================================================================
//processing the XML got from server
//===================================================================================================================================
private void processResponce(String responceFromServer)
{
try {
//saving the file as a xml
FileOutputStream fOut = openFileOutput("loginData.xml",MODE_WORLD_READABLE);
OutputStreamWriter osw = new OutputStreamWriter(fOut);
osw.write(responceFromServer);
osw.flush();
osw.close();
//reading the file as xml
FileInputStream fIn = openFileInput("loginData.xml");
InputStreamReader isr = new InputStreamReader(fIn);
char[] inputBuffer = new char[responceFromServer.length()];
isr.read(inputBuffer);
String readString = new String(inputBuffer);
//getting the xml Value as per child node form the saved xml
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
InputStream is = new ByteArrayInputStream(readString.getBytes("UTF-8"));
Document doc = db.parse(is);
NodeList root=doc.getElementsByTagName("root");
String loginStatus = null;
for (int i=0;i<root.getLength();i++)
{
loginStatus = "" + ((Element)root.item(i)).getAttribute("status");
}
//If Email and Pass match with server
if(loginStatus.equalsIgnoreCase("T"))
{
NodeList book=doc.getElementsByTagName("book");
List<String> url = new ArrayList<String>();
List<String> fileName = new ArrayList<String>();
List<String> bkId = new ArrayList<String>();
for (int i=0;i<book.getLength();i++)
{
url.add(((Element)book.item(i)).getAttribute("bookImageUrl"));
url.add(((Element)book.item(i)).getAttribute("pdfUrl"));
//------------------------------------------------------------------------------------------------------------
//Creating two list and storing image url, Book Id
//Logic
//This 2 list will be accessed and file name, pdf name, book id will be extracted from this 2 value and saved to local DB
//------------------------------------------------------------------------------------------------------------
fileName.add(((Element)book.item(i)).getAttribute("bookImageUrl"));
bkId.add(((Element)book.item(i)).getAttribute("bookId"));
}
String [] stringArray = url.toArray(new String[url.size()]);
//Array list is converted to String array
stringArrayBookId = bkId.toArray(new String[bkId.size()]);
stringArrayPdfUrlForLocalDB = fileName.toArray(new String[fileName.size()]);
// Toast.makeText( getApplicationContext(),"List Value:\n"+stringArrayPdfUrlForLocalDB.length,Toast.LENGTH_LONG).show();
new DownloadFileFromURL().execute(stringArray);
}
else if(loginStatus.equalsIgnoreCase("F"))
{
Toast.makeText( getApplicationContext(),"No Match found for this user",Toast.LENGTH_SHORT).show();
}
}
catch (Throwable t)
{
Toast.makeText( getApplicationContext(),""+t,Toast.LENGTH_SHORT).show();
Log.d("Error On Saving and reading", t+"");
}
}
主要活动
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/bg"
tools:context=".MainActivity" >
<GridView
android:id="@+id/gridview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:layout_marginTop="38sp"
android:columnWidth="80dp"
android:gravity="center"
android:numColumns="4"
android:stretchMode="columnWidth"
android:verticalSpacing="10dp"
android:listSelector="#00000000" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="40sp"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:background="@drawable/background_title"
android:orientation="vertical" >
<RelativeLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ImageView
android:id="@+id/lib_logo1"
android:layout_width="40sp"
android:layout_height="wrap_content"
android:layout_marginLeft="4sp"
android:src="@drawable/book" />
<ImageView
android:id="@+id/lib_logo2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@+id/lib_logo1"
android:src="@drawable/lib_icon" />
<ImageView
android:id="@+id/sync_img"
android:layout_width="50sp"
android:layout_height="50sp"
android:src="@drawable/sync"
android:layout_alignParentRight="true"
android:onClick="libSyc"/>
</RelativeLayout>
</LinearLayout>
答案 0 :(得分：0)
我猜ImageAdapter的问题
public Object getItem(int position) {
return null;
}
您需要返回给定位置的相应对象。返回近似对象。然后你的GridView包含所有对象为空，这就是为什么你变空（白色屏幕）。
答案 1 :(得分：0)
您正在尝试使用UI线程直接在适配器中加载图像，尝试在Android中使用Lazyloading概念在单独的线程中加载图像，这将解决问题。