我在这里有一个复选框的onClick方法：
@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 = mContext.getApplicationContext().openFileOutput("BitmapImage", Context.MODE_PRIVATE);
appBmp.compress(Bitmap.CompressFormat.JPEG, 80, out);
Log.i("AppInfoAdapter", "the icon(s) have been saved");
out.close();
// Load back the image file to confirm it works
// Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath() );
// ImageView imageV = (ImageView)findViewById(R.id.);
// imageV.setImageBitmap(bitmap);
}
catch (FileNotFoundException e1)
{
e1.printStackTrace();
}
catch (IOException e2)
{
e2.printStackTrace();
}
Intent intent = new Intent (v.getContext(), GVABackup.class);
v.getContext().startActivity(intent);
Log.i("AppInfoAdapter", "New intent started to send icon bitmap");
} else {
System.out.println("Un-Checked");
}
}
然后GVABackup.class就是这样：
package com.example.awesomefilebuilderwidget;
IMPORTS
public class GVABackup extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
ImageView view = (ImageView)findViewById(R.id.layout1);
Log.i("GridViewAdapter", "checkbox is checked");
FileInputStream in = null;
try {
in = openFileInput("BitmapImage");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// Load back the image file to confirm it works
Bitmap bitmap = BitmapFactory.decodeStream(in);
view.setImageBitmap(bitmap);
try {
in.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}}
另请注意我在gridView适配器中有这个类，这样我就可以从存储中获取位图，然后将其设置为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);
Log.d("GridViewAdapter", "new imageView added");
}
if(checked == true){
isSdReadable();
Intent intent = new Intent (view.getContext(), GVABackup.class);
view.getContext().startActivity(intent);
} else {
Log.e("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;
}
但是当我运行这段代码时，我得到了这个NPE：
12-14 16:04:51.197: I/System.out(3245): Checked
12-14 16:04:51.227: I/AppInfoAdapter(3245): the icon(s) have been saved
12-14 16:04:51.237: I/AppInfoAdapter(3245): New intent started to send icon bitmap
12-14 16:04:51.307: I/GridViewAdapter(3245): checkbox is checked
12-14 16:04:51.317: D/AndroidRuntime(3245): Shutting down VM
12-14 16:04:51.317: W/dalvikvm(3245): threadid=1: thread exiting with uncaught exception (group=0x4001d5a0)
12-14 16:04:51.347: E/AndroidRuntime(3245): FATAL EXCEPTION: main
12-14 16:04:51.347: E/AndroidRuntime(3245): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.awesomefilebuilderwidget/com.example.awesomefilebuilderwidget.GVABackup}: java.lang.NullPointerException
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1833)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1854)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.ActivityThread.access$1500(ActivityThread.java:135)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1041)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.os.Handler.dispatchMessage(Handler.java:99)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.os.Looper.loop(Looper.java:150)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.ActivityThread.main(ActivityThread.java:4333)
12-14 16:04:51.347: E/AndroidRuntime(3245): at java.lang.reflect.Method.invokeNative(Native Method)
12-14 16:04:51.347: E/AndroidRuntime(3245): at java.lang.reflect.Method.invoke(Method.java:507)
12-14 16:04:51.347: E/AndroidRuntime(3245): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-14 16:04:51.347: E/AndroidRuntime(3245): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-14 16:04:51.347: E/AndroidRuntime(3245): at dalvik.system.NativeStart.main(Native Method)
12-14 16:04:51.347: E/AndroidRuntime(3245): Caused by: java.lang.NullPointerException
12-14 16:04:51.347: E/AndroidRuntime(3245): at com.example.awesomefilebuilderwidget.GVABackup.onCreate(GVABackup.java:33)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1072)
12-14 16:04:51.347: E/AndroidRuntime(3245): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1797)
12-14 16:04:51.347: E/AndroidRuntime(3245): ... 11 more
这是第33行：
view.setImageBitmap(bitmap);
如此出色，“bitmap”正在返回null，这意味着我的FileInputStream没有得到任何东西......
我该如何解决这个问题？
请注意，“layout1”imageView应该是我的GridViewAdapter中的“view”imageView
答案 0 :(得分：0)
您必须在setContentView(layoutFileName.xml)行之后放置super.onCreate(savedInstanceState);， NPE ，因为没有加载 imageView ，因为没有xml文件引用此活动。