[英]Android Drawing Line with 2 points
Currently I'm developing an app, where line will be drawn from one point to another with button click on a bitmap. 目前我正在开发一个应用程序,通过按钮点击位图,将从一个点绘制到另一个点。 Here's my code in MainActivity.java: 这是我在MainActivity.java中的代码:
public class MainActivity extends Activity {
LineView lineview;
Button button;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//lineview = (LineView)findViewById (R.id.lineView1);
button = (Button)findViewById(R.id.btnCapture);
//lineview.setVisibility(View.INVISIBLE);
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// lineview.setVisibility(View.VISIBLE);
}
});
}
}
LineView.java - class that draws line LineView.java - 绘制线条的类
public class LineView extends View {
Paint paint = new Paint();
public LineView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public LineView(Context context, AttributeSet attrs, int defstyle) {
super(context, attrs, defstyle );
}
public LineView(Context context) {
super(context);
paint.setColor(Color.BLACK);
}
@Override
public void onDraw(Canvas canvas) {
canvas.drawLine(0, 0, 20, 20, paint);
}
}
Right now it draws the line from the start using defined coordinates. 现在,它使用定义的坐标从头开始绘制线条。 I want line to be drawn using coordinates from 2 points that get declared in main activity. 我希望使用在主要活动中声明的2个点的坐标绘制线。 And that function should work after onClick. 并且该功能应该在onClick之后工作。 Thanks in advance. 提前致谢。
You will have to create a custom view class that extends View
. 您必须创建一个扩展View
的自定义视图类。 Within that class you will override the onDraw
method which is passed a canvas. 在该类中,您将覆盖传递画布的onDraw
方法。 create a Paint
object and use it with the drawLine
function above. 创建一个Paint
对象并将其与上面的drawLine
函数一起使用。
I would suggest looking up Finger Paint app tutorials. 我建议查找Finger Paint应用程序教程。 There are at least a few online, and they are a good introduction to custom views and overriding the onDraw
method. 至少有几个在线,它们是对自定义视图的良好介绍并覆盖了onDraw
方法。
Use customview by extending the view class to achieve this: Let's call your custom class say LineView. 通过扩展视图类来实现这一点来使用customview:让我们调用你的自定义类说LineView。 So this is what Line should look like. 所以这就是Line应该是什么样子。
LineView.java LineView.java
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class LineView extends View {
Paint paint = new Paint();
public LineView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public LineView(Context context, AttributeSet attrs, int defstyle) {
super(context, attrs, defstyle );
}
public LineView(Context context) {
super(context);
paint.setColor(Color.BLACK);
}
@Override
public void onDraw(Canvas canvas) {
canvas.drawLine(0, 0, 20, 20, paint);
}
}
Now, you'll have to instantiate this in your mainactivity. 现在,您必须在mainactivity中实例化它。 You can do that using java code or xml. 你可以使用java代码或xml来做到这一点。 Using java code it will look like this: 使用java代码,它将如下所示:
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
public class MainActivity extends Activity {
LineView lineview;
Button button;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lineview = (LineView)findViewById (R.id.lineView1);
button = (Button)findViewById(R.id.button1);
lineview.setVisibility(View.INVISIBLE);
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
lineview.setVisibility(View.VISIBLE);
}
});
}
}
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