android - How to draw a circle on a Canvas

activity_main.xml 
 <?xml version="1.0" encoding="utf-8"?> <RelativeLayout     xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/rl"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:padding="16dp"     tools:context=".MainActivity"     android:background="#ffffff"     >     <ImageView         android:id="@+id/iv"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         />     <Button         android:id="@+id/btn"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="Draw Circle"         android:layout_alignParentRight="true"         android:layout_alignParentEnd="true"         android:layout_alignParentBottom="true"         /> </RelativeLayout>
MainActivity.java 
 package com.cfsuman.me.androidcode;  import android.content.Context; import android.content.res.Resources; import android.graphics.Color; import android.graphics.Paint; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.ImageView; import android.widget.RelativeLayout; import android.widget.TextView; import android.graphics.Canvas; import android.graphics.Bitmap;   public class MainActivity extends AppCompatActivity {     private Context mContext;     private Resources mResources;     private RelativeLayout mRelativeLayout;     private TextView mTextView;     private Button mButton;     private ImageView mImageView;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          // Get the application context         mContext = getApplicationContext();          // Get the Resources         mResources = getResources();          // Get the widgets reference from XML layout         mRelativeLayout = (RelativeLayout) findViewById(R.id.rl);         mButton = (Button) findViewById(R.id.btn);         mImageView = (ImageView) findViewById(R.id.iv);          // Set a click listener for Button widget         mButton.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View view) {                 // Initialize a new Bitmap object                 Bitmap bitmap = Bitmap.createBitmap(                         500, // Width                         300, // Height                         Bitmap.Config.ARGB_8888 // Config                 );                  // Initialize a new Canvas instance                 Canvas canvas = new Canvas(bitmap);                  // Draw a solid color to the canvas background                 canvas.drawColor(Color.LTGRAY);                  // Initialize a new Paint instance to draw the Circle                 Paint paint = new Paint();                 paint.setStyle(Paint.Style.FILL);                 paint.setColor(Color.RED);                 paint.setAntiAlias(true);                  // Calculate the available radius of canvas                 int radius = Math.min(canvas.getWidth(),canvas.getHeight()/2);                  // Set a pixels value to padding around the circle                 int padding = 5;                  /*                     public void drawCircle (float cx, float cy, float radius, Paint paint)                         Draw the specified circle using the specified paint. If radius is <= 0, then                         nothing will be drawn. The circle will be filled or framed based on the                         Style in the paint.                      Parameters                         cx : The x-coordinate of the center of the circle to be drawn                         cy : The y-coordinate of the center of the circle to be drawn                         radius : The radius of the cirle to be drawn                         paint : The paint used to draw the circle                 */                 // Finally, draw the circle on the canvas                 canvas.drawCircle(                         canvas.getWidth() / 2, // cx                         canvas.getHeight() / 2, // cy                         radius - padding, // Radius                         paint // Paint                 );                  // Display the newly created bitmap on app interface                 mImageView.setImageBitmap(bitmap);             }         });     } }
More android examples

Komentar

Posting Komentar