I have a class called CoverFlowClass. I used to do this to create a class,
CoverFlowClass coverFlow = new CoverFlowClass(this)
coverFlow.setAdapter(new ImageAdapter(this));
But now I want to use XML so I can do layouting. I create an XML code like this:
<id.co.ajsmsig.display.CoverFlowClass
android:id="@+id/coverflow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
But when I create from the code like this :
CoverFlowClass coverFlow= (CoverFlowClass) findViewById(R.id.coverflow);
coverFlow.setAdapter(new ImageAdapter(this));
My app force closed. The error log in LogCat i found is :
04-18 07:46:34.804: E/AndroidRuntime(1847): at id.co.ajsmsig.display.CoverFlowMain.onCreate(CoverFlowMain.java:76).
And the line 76 is :
coverFlow.setAdapter(new ImageAdapter(this));
I think because the class is using a parameter in it constructor (= new CoverFlowClass(this)) while findViewById does not give any parameter. I still have no idea, how to make this work? Any idea is appreciated.
Thanks
P.s. Below is the CoverFlow class source code:
package id.co.ajsmsig.display;
import android.content.Context;
import android.graphics.Camera;
import android.graphics.Matrix;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.Transformation;
import android.widget.Gallery;
import android.widget.ImageView;
public class CoverFlowClass extends Gallery {
/**
* Graphics Camera used for transforming the matrix of ImageViews
*/
private Camera mCamera = new Camera();
/**
* The maximum angle the Child ImageView will be rotated by
*/
private int mMaxRotationAngle = 60;
/**
* The maximum zoom on the centre Child
*/
private int mMaxZoom = -120;
/**
* The Centre of the Coverflow
*/
private int mCoveflowCenter;
public CoverFlowClass(Context context) {
super(context);
this.setStaticTransformationsEnabled(true);
}
public CoverFlowClass(Context context, AttributeSet attrs) {
super(context, attrs);
this.setStaticTransformationsEnabled(true);
}
public CoverFlowClass(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.setStaticTransformationsEnabled(true);
}
/**
* Get the max rotational angle of the image
* @return the mMaxRotationAngle
*/
public int getMaxRotationAngle() {
return mMaxRotationAngle;
}
/**
* Set the max rotational angle of each image
* @param maxRotationAngle the mMaxRotationAngle to set
*/
public void setMaxRotationAngle(int maxRotationAngle) {
mMaxRotationAngle = maxRotationAngle;
}
/**
* Get the Max zoom of the centre image
* @return the mMaxZoom
*/
public int getMaxZoom() {
return mMaxZoom;
}
/**
* Set the max zoom of the centre image
* @param maxZoom the mMaxZoom to set
*/
public void setMaxZoom(int maxZoom) {
mMaxZoom = maxZoom;
}
/**
* Get the Centre of the Coverflow
* @return The centre of this Coverflow.
*/
private int getCenterOfCoverflow() {
return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft();
}
/**
* Get the Centre of the View
* @return The centre of the given view.
*/
private static int getCenterOfView(View view) {
return view.getLeft() + view.getWidth() / 2;
}
/**
* {@inheritDoc}
*
* @see #setStaticTransformationsEnabled(boolean)
*/
protected boolean getChildStaticTransformation(View child, Transformation t) {
final int childCenter = getCenterOfView(child);
final int childWidth = child.getWidth() ;
int rotationAngle = 0;
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);
if (childCenter == mCoveflowCenter) {
transformImageBitmap((ImageView) child, t, 0);
} else {
rotationAngle = (int) (((float) (mCoveflowCenter - childCenter)/ childWidth) * mMaxRotationAngle);
if (Math.abs(rotationAngle) > mMaxRotationAngle) {
rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle;
}
transformImageBitmap((ImageView) child, t, rotationAngle);
}
return true;
}
/**
* This is called during layout when the size of this view has changed. If
* you were just added to the view hierarchy, you're called with the old
* values of 0.
*
* @param w Current width of this view.
* @param h Current height of this view.
* @param oldw Old width of this view.
* @param oldh Old height of this view.
*/
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
mCoveflowCenter = getCenterOfCoverflow();
super.onSizeChanged(w, h, oldw, oldh);
}
/**
* Transform the Image Bitmap by the Angle passed
*
* @param imageView ImageView the ImageView whose bitmap we want to rotate
* @param t transformation
* @param rotationAngle the Angle by which to rotate the Bitmap
*/
private void transformImageBitmap(View child, Transformation t, int rotationAngle) {
mCamera.save();
final Matrix imageMatrix = t.getMatrix();;
final int imageHeight = child.getLayoutParams().height;;
final int imageWidth = child.getLayoutParams().width;
final int rotation = Math.abs(rotationAngle);
mCamera.translate(0.0f, 0.0f, 100.0f);
//As the angle of the view gets less, zoom in
if ( rotation < mMaxRotationAngle ) {
float zoomAmount = (float) (mMaxZoom + (rotation * 1.5));
mCamera.translate(0.0f, 0.0f, zoomAmount);
}
mCamera.rotateY(rotationAngle);
mCamera.getMatrix(imageMatrix);
imageMatrix.preTranslate(-(imageWidth/2), -(imageHeight/2));
imageMatrix.postTranslate((imageWidth/2), (imageHeight/2));
mCamera.restore();
}
}
It sounds like you have a NullPointerException: the findViewById call does not actually find the View, because it is never instantiated. You probably need to implement a constructor for CoverFlowClass that takes in an `AttributeSet. Perhaps like so:
public CoverFlowClass(Context context, AttributeSet attrs)
{
super(context, attrs);
// do whatever other initialization is necessary
}