Android之拖拉功能
1：ColorBall?
package cn.itcast.dragdrop;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Point;public class ColorBall { private Bitmap img; // the image of the ball private int coordX = 0; // the x coordinate at the canvas private int coordY = 0; // the y coordinate at the canvas private int id; // gives every ball his own id, for now not necessary private static int count = 1; private boolean goRight = true; private boolean goDown = true; public ColorBall(Context context, int drawable) {BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inJustDecodeBounds = true; img = BitmapFactory.decodeResource(context.getResources(), drawable); id=count;count++;}public ColorBall(Context context, int drawable, Point point) {BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inJustDecodeBounds = true; img = BitmapFactory.decodeResource(context.getResources(), drawable); id=count;count++;coordX= point.x;coordY = point.y;}public static int getCount() {return count;}void setX(int newValue) { coordX = newValue; }public int getX() {return coordX;}void setY(int newValue) { coordY = newValue; }public int getY() {return coordY;}public int getID() {return id;}public Bitmap getBitmap() {return img;}public void moveBall(int goX, int goY) {// check the borders, and set the direction if a border has reachedif (coordX > 270){goRight = false;}if (coordX < 0){goRight = true;}if (coordY > 400){goDown = false;}if (coordY < 0){goDown = true;}// move the x and y if (goRight){coordX += goX;}else{coordX -= goX;}if (goDown){coordY += goY;}else{coordY -= goY;}}}?
2：DrawView
package cn.itcast.dragdrop;import android.content.Context;import android.graphics.Canvas;import android.graphics.Point;import android.view.MotionEvent;import android.view.View;public class DrawView extends View { private ColorBall[] colorballs = new ColorBall[3]; // array that holds the balls private int balID = 0; // variable to know what ball is being dragged public DrawView(Context context) { super(context); setFocusable(true); //necessary for getting the touch events // setting the start point for the balls Point point1 = new Point(); point1.x = 50; point1.y = 20; Point point2 = new Point(); point2.x = 100; point2.y = 20; Point point3 = new Point(); point3.x = 150; point3.y = 20; // declare each ball with the ColorBall class colorballs[0] = new ColorBall(context,R.drawable.bol_groen, point1); colorballs[1] = new ColorBall(context,R.drawable.bol_rood, point2); colorballs[2] = new ColorBall(context,R.drawable.bol_blauw, point3); } // the method that draws the balls @Override protected void onDraw(Canvas canvas) { //canvas.drawColor(0xFFCCCCCC); //if you want another background color //draw the balls on the canvas for (ColorBall ball : colorballs) { canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(), null); } } // events when touching the screen public boolean onTouchEvent(MotionEvent event) { int X = (int)event.getX(); int Y = (int)event.getY(); switch (event.getAction() ) { case MotionEvent.ACTION_DOWN: // touch down so check if the finger is on a ball balID = 0; for (ColorBall ball : colorballs) { // check if inside the bounds of the ball (circle) // get the center for the ball int centerX = ball.getX() + 25; int centerY = ball.getY() + 25; // calculate the radius from the touch to the center of the ball double radCircle = Math.sqrt( (double) (((centerX-X)*(centerX-X)) + (centerY-Y)*(centerY-Y))); // if the radius is smaller then 23 (radius of a ball is 22), then it must be on the ball if (radCircle < 23){ balID = ball.getID(); break; } // check all the bounds of the ball (square) //if (X > ball.getX() && X < ball.getX()+50 && Y > ball.getY() && Y < ball.getY()+50){ //balID = ball.getID(); //break; //} } break; case MotionEvent.ACTION_MOVE: // touch drag with the ball // move the balls the same as the finger if (balID > 0) { colorballs[balID-1].setX(X-25); colorballs[balID-1].setY(Y-25); } break; case MotionEvent.ACTION_UP: // touch drop - just do things here after dropping break; } // redraw the canvas invalidate(); return true; }}?
3：MainActivity
package cn.itcast.dragdrop;import android.app.Activity;import android.os.Bundle;public class MainActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new DrawView(this)); }}?
4：
<?xml version="1.0" encoding="utf-8" ?> - <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="cn.itcast.dragdrop" android:versionCode="1" android:versionName="1.0">- <application android:icon="@drawable/icon" android:label="@string/app_name">- <activity android:name=".MainActivity" android:label="@string/app_name">- <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-sdk android:minSdkVersion="7" /> </manifest>
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