我的GridViewAdapter类中有一个imageView：
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// Try to reuse the views
ImageView view = (ImageView) convertView;
boolean checked = (mCheckBox==null)?false:(((CheckBox) mCheckBox).isChecked());
// if convert view is null then create a new instance else reuse it
if (view == null) {
view = new ImageView(Context);
view.setId(1);
Log.d("GridViewAdapter", "new imageView added");
}
然后我在这里尝试将位图设置为另一个类中的imageView（view）：
@Override
public void onClick(View v) {
if (addCheckbox.isChecked()) {
System.out.println("Checked");
PackageManager pm = mContext.getPackageManager();
final int DEST_IMAGE_WIDTH = 100;
final int DEST_IMAGE_HEIGHT = 100;
ApplicationInfo appInfo = mContext.getApplicationInfo();
Drawable appIcon = pm.getApplicationIcon(appInfo);
Bitmap appBmp = Bitmap.createBitmap(DEST_IMAGE_WIDTH, DEST_IMAGE_HEIGHT, Config.ARGB_8888);
// Creates a new canvas based on the image specification
// created just above.
Canvas canvas = new Canvas(appBmp);
// (optional) Fills the entire canvas
canvas.drawColor(Color.WHITE);
// You need to set bounds otherwise a 0,0 sized image would be drawn.
appIcon.setBounds(0, 0, DEST_IMAGE_WIDTH, DEST_IMAGE_HEIGHT);
appIcon.draw(canvas);
/// Let's save to a .jpg file ...
File file = new File(mContext.getFilesDir().getAbsolutePath() + "/test2.jpg");
FileOutputStream out;
try
{
file.createNewFile();
out = new FileOutputStream(file);
appBmp.compress(Bitmap.CompressFormat.JPEG, 80, out);
out.close();
// Load back the image file to confirms it works
Bitmap bitmap = BitmapFactory.decodeFile( file.getAbsolutePath() );
ImageView imageView1 = (ImageView)v.findViewById(1);
imageView1.setImageBitmap( bitmap );
}
但是我得到了这个NPE：
12-22 15:58:45.782: E/AndroidRuntime(28793): FATAL EXCEPTION: main
12-22 15:58:45.782: E/AndroidRuntime(28793): java.lang.NullPointerException
12-22 15:58:45.782: E/AndroidRuntime(28793): at com.example.awesomefilebuilderwidget.AppInfoAdapter$1.onClick(AppInfoAdapter.java:200)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.view.View.performClick(View.java:2532)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.widget.CompoundButton.performClick(CompoundButton.java:99)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.view.View$PerformClick.run(View.java:9308)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.os.Handler.handleCallback(Handler.java:587)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.os.Handler.dispatchMessage (Handler.java:92)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.os.Looper.loop(Looper.java:150)
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.app.ActivityThread.main(ActivityThread.java:4333)
12-22 15:58:45.782: E/AndroidRuntime(28793): at java.lang.reflect.Method.invokeNative(Native Method)
12-22 15:58:45.782: E/AndroidRuntime(28793): at java.lang.reflect.Method.invoke(Method.java:507)
12-22 15:58:45.782: E/AndroidRuntime(28793): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-22 15:58:45.782: E/AndroidRuntime(28793): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-22 15:58:45.782: E/AndroidRuntime(28793): at dalvik.system.NativeStart.main(Native Method)
这是第200行：
imageView1.setImageBitmap( bitmap );
显然我的imageView正在返回null
我猜我没有正确设置ID和/或使用不正确？
如何解决此问题NPE？
增加：
这是我的完整适配器类（GridViewAdapter）：
package com.example.awesomefilebuilderwidget;
IMPORTS
public class GridViewAdapter extends BaseAdapter {
private Context Context;
// Keep all Images in array list
public ArrayList<Integer> drawables = new ArrayList<Integer>();
CheckBox mCheckBox=null;
// Constructor
public GridViewAdapter(Context c){
Context = c;
Log.d("GridViewAdapter", "Constructor is set");
drawables.add(R.drawable.pattern1);
Log.d("GridViewAdapter", "pattern1 added");
drawables.add(R.drawable.pattern2);
Log.d("GridViewAdapter", "pattern2 added");
drawables.add(R.drawable.trashcan);
Log.d("GridViewAdapter", "trashcan added");
drawables.add(R.drawable.ic_launcher);
Log.d("GridViewAdapter", "ic_launcher added");
}
public void setCheckBox(CheckBox checkbox){
mCheckBox=checkbox;
}
@Override
// How many items are in the data set represented by this Adapter
public int getCount() {
return drawables.size();
}
@Override
// Get the data item associated with the specified position in the
// data set
public Object getItem(int position) {
return drawables.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public boolean isSdReadable() {
boolean mExternalStorageAvailable = false;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
// We can read and write the media
mExternalStorageAvailable = true;
Log.i("isSdReadable", "External storage card is readable.");
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
// We can only read the media
Log.i("isSdReadable", "External storage card is readable.");
mExternalStorageAvailable = true;
} else {
// Something else is wrong. It may be one of many other
// states, but all we need to know is we can neither read nor write
mExternalStorageAvailable = false;
}
return mExternalStorageAvailable;
}
public Bitmap getThumbnail() {
final String APP_PATH_SD_CARD = "/TEST/";
final String APP_THUMBNAIL_PATH_SD_CARD = "thumbnails";
String filename = "AFBWIcon.png";
String fullPath = Environment.getExternalStorageDirectory().getAbsolutePath() + APP_PATH_SD_CARD + APP_THUMBNAIL_PATH_SD_CARD;
Bitmap thumbnail = null;
// Look for the file on the external storage
try {
if (isSdReadable() == true) {
thumbnail = BitmapFactory.decodeFile(fullPath + "/" + filename);
}
} catch (Exception e) {
Log.e("getThumbnail() on external storage", e.getMessage());
}
// If no file on external storage, look in internal storage
if (thumbnail == null) {
try {
File filePath = Context.getFileStreamPath(filename);
FileInputStream fi = new FileInputStream(filePath);
thumbnail = BitmapFactory.decodeStream(fi);
} catch (Exception ex) {
Log.e("getThumbnail() on internal storage", ex.getMessage());
}
}
return thumbnail;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// Try to reuse the views
ImageView view = (ImageView) convertView;
boolean checked = (mCheckBox==null)?false:(((CheckBox) mCheckBox).isChecked());
// if convert view is null then create a new instance else reuse it
if (view == null) {
view = new ImageView(Context);
//view.setTag(ViewId(), "imageViewGRID");
view.setId(1);
Log.d("GridViewAdapter", "new imageView added");
}
if(checked == true){
isSdReadable();
Log.i("GridViewAdapter", "checkbox is checked");
} else {
Log.i("GridView", "Icons not for use/checkbox not checked");
}
view.setImageResource(drawables.get(position));
view.setScaleType(ImageView.ScaleType.CENTER_CROP);
view.setLayoutParams(new android.widget.GridView.LayoutParams(70, 70));
view.setTag(String.valueOf(position));
return view;
}
}
答案 0 :(得分：0)
ImageView imageView1 = (ImageView)v.findViewById(1);
这是怎么回事？ 你不应该有这样的东西让它起作用：
ImageView imageView1 = (ImageView)v.findViewById(R.id.example);
您需要为findViewById