一手遮天 Android - 輸入: Touch 簡單的塗鴉闆
項目位址 https://github.com/webabcd/AndroidDemo
作者 webabcd
示例如下:
/input/TouchDemo5.java
/**
* Touch 簡單的塗鴉闆
*
*
* 本例示範了如何實作一個簡單的塗鴉闆控件(參見 view/input/TouchDemo5_CustomView.java)
*/
package com.webabcd.androiddemo.input;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.webabcd.androiddemo.R;
public class TouchDemo5 extends AppCompatActivity {
private TouchDemo5_CustomView mCustomView1;
private Button mButton1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_input_touchdemo5);
mCustomView1 = findViewById(R.id.customView1);
mButton1 = findViewById(R.id.button1);
sample();
}
private void sample() {
mButton1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// 清除塗鴉闆控件中的内容
mCustomView1.clear();
}
});
}
}
/**
* 自定義控件,實作了簡單的塗鴉功能
*/
package com.webabcd.androiddemo.input;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
public class TouchDemo5_CustomView extends View {
private Paint mPaint;
private Path mPath;
private float mX;
private float mY;
public TouchDemo5_CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
private void init() {
mPaint = new Paint();
mPaint.setAntiAlias(true); // 消除鋸齒
mPaint.setStrokeWidth(5);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(Color.BLACK);
mPath = new Path();
}
@Override
protected void onDraw(Canvas canvas) {
// 繪制塗鴉
canvas.drawPath(mPath, mPaint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mX = x;
mY = y;
// 指定 path 的起點
mPath.moveTo(mX, mY);
break;
case MotionEvent.ACTION_MOVE:
// 用二次貝塞爾曲線連接配接 path 的每一點
mPath.quadTo(mX, mY, x, y);
mX = x;
mY = y;
break;
case MotionEvent.ACTION_UP:
break;
}
// 調用 draw()
invalidate();
return true;
}
// 清除塗鴉
public void clear() {
mPath.reset();
// 調用 draw()
invalidate();
}
}
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="清除" />
<!--
實作了簡單塗鴉功能的自定義控件
-->
<com.webabcd.androiddemo.input.TouchDemo5_CustomView
android:id="@+id/customView1"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>