Android利用canvas画画板
Android利用canvas画画板，首先新建一个项目工程，建立文件，如下图所示
首先配置页面布局文件activity_main.xml，如下图所示：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageView
android:id="@+id/iv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@drawable/bg"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="画笔的粗细"
/>
<SeekBar
android:id="@+id/sb"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:max="256"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="颜色"
/>
<Spinner
android:id="@+id/sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:entries="@array/color"
/>
<Button
android:id="@+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="保存"
/>
</LinearLayout>
然后书写主页的代码MainActivity.java代码如下
package com.xunfang.drawing;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.MonthDisplayHelper;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.Spinner;
import android.widget.Toast;
public class MainActivity extends Activity {
private SeekBar sb;
private ImageView iv;
private Button btn;
private Spinner sp;
private String[] color ;
private Bitmap bm;
private Bitmap copy;
private Canvas canvas;
private Paint paint;
private File file;
private int yanse;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//拿到在xml文件中定义的颜色数组
color = getResources().getStringArray(R.array.color) ;
//实例化
initData();
//设置监听器
setLister();
//画画
loadingImage();
}
private void loadingImage() {
// 加载原始图片
bm = BitmapFactory.decodeResource(getResources(), R.drawable.bg);
// 需要创建一个和原始的图片大小一样的空白图片(一张纸,上面没有任何数据)
copy = bm.createBitmap(bm.getWidth(), bm.getHeight(), bm.getConfig());
// 需要一个画板,画板上铺上白纸
canvas= new Canvas(copy);
// 创建画笔
paint= new Paint();
// 给imageView空间加载一个滑动监听器
iv.setOnTouchListener(new OnTouchListener() {
int startx;
int starty;
@Override
public boolean onTouch(View v, MotionEvent event) {
// 拿到动作
int type = event.getAction();
switch (type) {
case MotionEvent.ACTION_DOWN:
startx = (int) event.getX();
starty = (int) event.getY();
break;
case MotionEvent.ACTION_MOVE:
int endx = (int) event.getX();
int endy = (int) event.getY();
//画画
canvas.drawLine(startx, starty, endx, endy, paint);
startx = (int) event.getX();
starty = (int) event.getY();
iv.setImageBitmap(copy);
break;
case MotionEvent.ACTION_UP:
break;
}
return true;
}
});
}
private void setLister() {
//下拉框
sp.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
Toast.makeText(getApplicationContext(), "你点击的是：" + color[position], 0).show();
switch (position) {
case 1:
paint.setColor(Color.GREEN);
break;
case 2:
paint.setColor(Color.BLUE);
break;
case 3:
paint.setColor(Color.BLACK);
break;
case 4:
paint.setColor(Color.YELLOW);
break;
case 0:
paint.setColor(Color.RED);
break;
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
//保存
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
try {
//指定图片的存储路径
file = new File(Environment.getExternalStorageDirectory().getAbsoluteFile()+"/draw.png");
FileOutputStream fos = new FileOutputStream(file);
copy.compress(CompressFormat.PNG, 100, fos);
Toast.makeText(getApplicationContext(), "保存成功", 0).show() ;
} catch (Exception e) {
}
//欺骗系统,告诉系统插入一个sd卡
Intent intent = new Intent();
intent.setAction(intent.ACTION_MEDIA_MOUNTED);
intent.setData(Uri.fromFile(file));
sendBroadcast(intent);
}
});
}
private void initData() {
sb = (SeekBar) findViewById(R.id.sb);
btn = (Button) findViewById(R.id.btn);
sp = (Spinner) findViewById(R.id.sp);
iv = (ImageView) findViewById(R.id.iv);
}
}
AndroidManifest.xml配置文件如下：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.xunfang.drawing"
android:versionCode="1"
android:versionname="1.0" >
<uses-sdk
android:minSdkVersion="16"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<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>
</manifest>
然后用虚拟机测试如下所示：
可以在模拟器看一下，生成的文件
表示验证成功了