Android利用canvas畫畫板，首先新建一個項目工程，建立文件，如下圖所示
首先配置頁面布局文件activity_main.xml，如下圖所示：
<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="畫筆的粗細"
/>
<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="顏色"
/>
<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>
然後書寫主頁的代碼MainActivity.java代碼如下
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文件中定義的顏色數組
color = getResources().getStringArray(R.array.color) ;
//實例化
initData();
//設置監聽器
setLister();
//畫畫
loadingImage();
}
private void loadingImage() {
// 加載原始圖片
bm = BitmapFactory.decodeResource(getResources(), R.drawable.bg);
// 需要創建一個和原始的圖片大小一樣的空白圖片(一張紙,上面沒有任何數據)
copy = bm.createBitmap(bm.getWidth(), bm.getHeight(), bm.getConfig());
// 需要一個畫板,畫板上鋪上白紙
canvas= new Canvas(copy);
// 創建畫筆
paint= new Paint();
// 給imageView空間加載一個滑動監聽器
iv.setOnTouchListener(new OnTouchListener() {
int startx;
int starty;
@Override
public boolean onTouch(View v, MotionEvent event) {
// 拿到動作
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();
//畫畫
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(), "你點擊的是：" + 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 {
//指定圖片的存儲路徑
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) {
}
//欺騙系統,告訴系統插入一個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>
然後用虛擬機測試如下所示：
可以在模擬器看一下，生成的文件
表示驗證成功了
更多Android相關信息見Android 專題頁面 http://www.linuxidc.com/topicnews.aspx?tid=11