Android画画板的制作方法

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"  android:layout_width="match_parent" android:layout_height="match_parent"  tools:context="com.example.demo.MainActivity">  <ImageView    android:id="@+id/iv"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:src="@drawable/bg"    />  <LinearLayout    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:orientation="horizontal"    android:layout_alignParentBottom="true"    >    <Button      android:id="@+id/red"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="红色"      android:onClick="onplay"      />    <Button      android:id="@+id/green"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="绿色"      android:onClick="onplay"      />    <Button      android:id="@+id/root"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="刷子"      android:onClick="onplay"      />    <Button      android:id="@+id/save"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="保存"      android:onClick="onplay"      />    <Button      android:id="@+id/finish"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="涂漆"      android:onClick="onplay"      />  </LinearLayout></RelativeLayout>

/*画板canvas  画板paint 手势识别器整体思路:因为我是图片是作画,实际是对图片进行修改,起到画图的效果1.原图,白纸,画笔,画板2.根据手势识别进行作画 */public class MainActivity extends AppCompatActivity {private Bitmap bitmap;  private Canvas canvas;private ImageView iv;  private int startx;  private int starty;  private Paint paint;  private Bitmap bmSrc;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    //加载原图    bmSrc = BitmapFactory.decodeResource(getResources(), R.drawable.bg);    //创建白纸,宽,高,图片的参数     bitmap = Bitmap.createBitmap(bmSrc.getWidth(), bmSrc.getHeight(), bmSrc.getConfig());    //创建画板,参数是白纸对象    canvas = new Canvas(bitmap);    //创建画笔    paint = new Paint();    //在纸上作画    iv=(ImageView)findViewById(R.id.iv);    canvas.drawBitmap(bmSrc,new Matrix(), paint);    //-----------------手势识别器和画笔结合的知识-------------------  //给控件设置手势适配器,可以得到用户在这个控件上所做的手势    iv.setOnTouchListener(new View.OnTouchListener() {      //当用户手在这个控件时,指的就是用户的手对控件滑动,按下,松开的三种场景,自动回调      @Override      public boolean onTouch(View view, MotionEvent motionEvent) {        switch (motionEvent.getAction()){          case MotionEvent.ACTION_DOWN://按下时回调一次            //获取用户手指按下时的坐标            startx = (int) motionEvent.getX();            starty = (int) motionEvent.getY();            break;          case MotionEvent.ACTION_MOVE://手指滑动时,不停地调用            int newx = (int) motionEvent.getX();            int newy = (int) motionEvent.getY();            //在背景图画线            canvas.drawLine(startx,starty,newx,newy, paint);            startx=newx;            starty=newy;            iv.setImageBitmap(bitmap);            break;          case MotionEvent.ACTION_UP://松开时回调一次            break;        }        //事情分发机制        //true:iv处理该触摸事件        //false:iv不处理该触摸事件,事件传递给上一级        return true;      }    });  }  public void onplay(View view){   switch (view.getId()){     case R.id.red:       paint.setColor(Color.RED);       break;     case R.id.green:       paint.setColor(Color.GREEN);       break;     case R.id.root:       paint.setStrokeWidth(5);       break;     case R.id.save:       if(SaveViewUtil.saveScreen(iv)){         Toast.makeText(this, "截图成功", Toast.LENGTH_SHORT).show();       }else{         Toast.makeText(this, "截图失败，请检查sdcard是否可用", Toast.LENGTH_SHORT).show();       }       break;     //涂漆     case R.id.finish:       canvas.drawRect(new Rect(0,0,width,height), paint);       break;     }   }  }

public class SaveViewUtil {    private static final File rootDir = new File(Environment.getExternalStorageDirectory()+File.separator);  /**保存截图的方法*/  public static boolean saveScreen(View view){   //判断sdcard是否可用   if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){     return false;   }   if(!rootDir.exists()){     rootDir.mkdir();   }   view.setDrawingCacheEnabled(true);   view.buildDrawingCache();   Bitmap bitmap = view.getDrawingCache();   try {     bitmap.compress(CompressFormat.JPEG, 100, new FileOutputStream(new File(rootDir,System.currentTimeMillis()+".jpg")));     return true;   } catch (FileNotFoundException e) {     e.printStackTrace();     return false;   }finally{     view.setDrawingCacheEnabled(false);     bitmap = null;   }  }}<!-- 往SDCard写入数据权限 --><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>