Android：嘿，我想检索屏幕的宽度并将其除以 3。我想在 LayoutParams 中使用这个长度，但它不起作用。我究竟做错了什么 ？应用程序在 // 1 崩溃。
public class LoaderImageView extends LinearLayout {
private Context mContext;
private Drawable mDrawable;
private ProgressBar mSpinner;
private ImageView mImage;
Context ctx;
Display display;
public LoaderImageView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public LoaderImageView(Context context) {
super(context);
init(context);
}
/**
* First time loading of the LoaderImageView
* Sets up the LayoutParams of the view, you can change these to
* get the required effects you want
*/
private void init(final Context context) {
mContext = context;
//1. //这是应用程序崩溃，从这里开始
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int width = size.x;
int height = size.y;
// 到这里
mImage = new ImageView(mContext);
mImage.setLayoutParams(new LayoutParams((width/3), 150));
mImage.setVisibility(View.GONE);
mImage.setBackgroundColor(Color.WHITE);
mImage.setPadding(3, 3, 3, 3);
mSpinner = new ProgressBar(mContext);
mSpinner.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
mSpinner.setIndeterminate(true);
addView(mSpinner);
addView(mImage);
}
/**
* Set's the view's drawable, this uses the internet to retrieve the image
* don't forget to add the correct permissions to your manifest
*
* @param imageUrl the url of the image you wish to load
*/
public void setImageDrawable(final String imageUrl) {
mDrawable = null;
mSpinner.setVisibility(View.VISIBLE);
mImage.setVisibility(View.GONE);
new Thread() {
public void run() {
try {
mDrawable = getDrawableFromUrl(imageUrl);
imageLoadedHandler.sendEmptyMessage(RESULT_OK);
} catch (MalformedURLException e) {
imageLoadedHandler.sendEmptyMessage(RESULT_CANCELED);
} catch (IOException e) {
imageLoadedHandler.sendEmptyMessage(RESULT_CANCELED);
}
};
}.start();
}
/**
* Callback that is received once the image has been downloaded
*/
private final Handler imageLoadedHandler = new Handler(new Callback() {
public boolean handleMessage(Message msg) {
switch (msg.what) {
case RESULT_OK:
mImage.setImageDrawable(mDrawable);
mImage.setVisibility(View.VISIBLE);
mSpinner.setVisibility(View.GONE);
break;
case RESULT_CANCELED:
default:
// Could change image here to a 'failed' image
// otherwise will just keep on spinning
break;
}
return true;
}
});
/**
* Pass in an image url to get a drawable object
*
* @return a drawable object
* @throws IOException
* @throws MalformedURLException
*/
private static Drawable getDrawableFromUrl(final String url) throws IOException, MalformedURLException {
return Drawable.createFromStream(((java.io.InputStream) new java.net.URL(url).getContent()), "name");
}
}