Young man, it’s time to create your first cool 3D effect!

Background

There are two Camera classes in Android. One is android.hardware.Camera, which is used to operate the device's camera. The other is android.graphics.Camera, which can be used to perform 3D transformations and then apply the transformed matrix Matrix to Canvas, etc. This article will introduce this Camera class.

Camera

As we mentioned before, Camera is a class that can perform 3D transformations. After performing 3D transformations, we can assign the transformation matrix Matrix through mCamera.getMatrix(Matrix) and then use it on Canvas. Alternatively, you can directly apply the transformation to a Canvas through mCamera.applyToCanvas(Canvas).

Three-dimensional coordinate axes in Android

The 3D coordinate axes in Android conform to the left-handed coordinate system.

The default position of the Camera is (0, 0, -8).

Camera transformation operations

Camera does not have many methods, so it is relatively simple and clear to use.

Camera usage examples

Since the core of using Camera is to obtain a transformed Matrix, you need to have a certain understanding of Matrix.

Demo1

3D ViewGroup Demo

Camera is used for custom animation

Here is a code example. The usage is essentially the same as the previous example. Both use the Camera transformation to obtain the Matrix matrix.

 public class Custom3DAnimation extends Animation { 
 
 
 private Camera mCamera; 
 
 private int centerWidth; 
 
 private int centerHeight; 
 
 
 public void setmRotateY( float mRotateY) { 
 
        this.mRotateY = mRotateY; 
 
 } 
 
 
 private float mRotateY; 
 
 
 public Custom3DAnimation() { 
 
        mCamera = new Camera(); 
 
 mRotateY = 90; 
 
 } 
 
 
 @Override 
 
    protected void applyTransformation( float interpolatedTime, Transformation t) { 
 
 Matrix matrix = t.getMatrix(); //Get the Transformation Matrix 
 
 mCamera.save(); //Save the current lens status 
 
 mCamera.rotateY(mRotateY * interpolatedTime); //Rotate the camera 
 
 mCamera.getMatrix(matrix); //Apply the rotation transformation to the matrix 
 
 mCamera.restore(); //Merge lens layer 
 
 matrix.preTranslate(centerWidth, centerHeight); //Translate before operation 
 
 matrix.postTranslate(-centerWidth, -centerHeight); //Translate after operation 
 
 
 } 
 
 
 @Override 
 
 public void initialize( int width, int height, int parentWidth, int parentHeight) { 
 
        super.initialize(width, height, parentWidth, parentHeight); 
 
 setDuration(5 * 1000); //Set the default duration 
 
 setFillAfter( true ); //Set whether to keep the state after the animation ends 
 
 setInterpolator(new LinearInterpolator()); //Set the interpolator 
 
        centerWidth = width / 2; 
 
                centerHeight = height / 2; 
 
 } 
 
 }

Summarize

The use of Camera is not complicated. You just need to remember the methods mentioned above. Since Camera eventually outputs a matrix, you also need to have a certain understanding of the matrix. I have given a quick guide to using the matrix above, and you can refer to it according to your situation.