我想在 MainActivity.java 中绘制一个矩形，但我的代码无法在主 Activity 中绘制一个矩形

Question

I want draw a rectangle in MainActivity.java but my code can not draw a rectangle and I added only the following function

public boolean draw(Canvas canvas)

it runs successfully but it can not draw a rectangle in main Activity.

package com.examplee.pro;

import android.os.Bundle; import android.app.Activity; import android.view.Menu; import android.graphics.*;

public class MainActivity extends Activity {

 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } public boolean draw(Canvas canvas){ Paint o = new Paint(); o.setColor(0); canvas.drawRect(100,100,100,100,o); return true; } }

Where is the problem?

Answer 1

What you need to do is to write your code in the onDraw method.

Although, I am not sure how you can use the canvas.I am sure you can but I never used it.However, here is a helpful link that will get your job done for sure.Just take the time and read it,everything is detailed and clear!

http://developer.android.com/reference/android/graphics/Rect.html