Android简单实现画图功能

前端技术 2023/09/07 Android

如何在图片上画画呢？这里写了一个demo，供大家参考
一、先看一眼工程结构
工程结构：

二、自定义view
这个自定义view实现了保留轨迹的功能，代码如下

package picturegame.view; 
 
import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Paint.Style; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.view.View; 
import com.winton.picturegame.R; 
 
public class GameView extends View{ 
   
  private Paint paint = null; // 
   
  private Bitmap originalBitmap = null;//原始图 
   
  private Bitmap new1Bitmap = null; 
   
  private Bitmap new2Bitmap = null; 
   
  private float clickX =0; 
   
  private float clickY=0; 
   
  private float startX=0; 
   
  private float startY=0; 
   
  private boolean isMove = true; 
   
  private boolean isClear = false; 
   
  private int color =Color.RED;//默认画笔颜色为红色 
   
  private float strokeWidth =2.0f;//默认画笔粗度 
   
   
 
  public GameView(Context context) { 
    this(context,null); 
    // TODO Auto-generated constructor stub 
  } 
  public GameView(Context context,AttributeSet atts) { 
    this(context,atts,0); 
    // TODO Auto-generated constructor stub 
  } 
  public GameView(Context context,AttributeSet atts,int defStyle) { 
    super(context,atts,defStyle); 
    // TODO Auto-generated constructor stub 
     
    originalBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.default_pic).copy(Bitmap.Config.ARGB_8888, true);//加载一张背景 
    new1Bitmap=originalBitmap.createBitmap(originalBitmap); 
  } 
 
  //清除函数 
  public void clear(){ 
    isClear =true; 
    new2Bitmap=originalBitmap.createBitmap(originalBitmap); 
    invalidate();//重载 
  } 
   
  public void setStrokeWidth(float width){ 
    this.strokeWidth=width; 
    initPaint(); 
  } 
  @Override 
  protected void onDraw(Canvas canvas) { 
    // TODO Auto-generated method stub 
    super.onDraw(canvas); 
    canvas.drawBitmap(writer(new1Bitmap),0,0, null); 
     
  } 
   
  @Override 
  public boolean onTouchEvent(MotionEvent event) { 
    // TODO Auto-generated method stub 
     
     
    clickX =event.getX(); 
     
    clickY=event.getY(); 
     
    if(event.getAction()==MotionEvent.ACTION_DOWN){ 
      isMove =false; 
      invalidate(); 
      return true; 
    } 
    else if(event.getAction()==MotionEvent.ACTION_MOVE){ 
      isMove =true; 
      invalidate(); 
      return true; 
    } 
     
     
    return super.onTouchEvent(event); 
  } 
   
  /** 
  * @Title: writer 
  * @Description: TODO(生成bitmap) 
  * @param @param pic 
  * @param @return  设定文件 
  * @return Bitmap  返回类型 
  * @throws 
  */ 
  public Bitmap writer(Bitmap pic){ 
    initPaint(); 
     
    Canvas canvas =null; 
    if(isClear){ 
      canvas=new Canvas(new2Bitmap); 
    }else{ 
      canvas=new Canvas(pic); 
    } 
     
    if(isMove){ 
      canvas.drawLine(startX, startY, clickX, clickY, paint);//划线 
    } 
    startX = clickX; 
     
    startY =clickY; 
    if(isClear){ 
      return new2Bitmap; 
    } 
    return pic; 
  } 
   
  private void initPaint(){ 
     
    paint = new Paint();//新建画笔 
     
    paint.setStyle(Style.STROKE);//设置为画线 
     
    paint.setAntiAlias(true);//可以让线条圆滑一些 
     
    paint.setColor(color);//设置画笔颜色 
     
    paint.setStrokeWidth(strokeWidth);//设置画笔线条的粗细 
  } 
   
  /** 
  * @Title: setColor 
  * @Description: TODO(设置线条颜色的对外接口) 
  * @param @param color  设定文件 
  * @return void  返回类型 
  * @throws 
  */ 
  public void setColor(int color){ 
     
    this.color=color; 
    initPaint(); 
  } 
   
   
}


三、主页面布局文件
主页面布局文件

<LinearLayout xmlns:android=\"http://schemas.android.com/apk/res/android\" 
  android:layout_width=\"fill_parent\" 
  android:layout_height=\"fill_parent\" 
  android:gravity=\"center_horizontal\" 
  android:orientation=\"vertical\" > 
   
  <LinearLayout  
    android:layout_width=\"match_parent\" 
    android:layout_height=\"50dp\"  
    android:orientation=\"horizontal\"    
    > 
    <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_30\" 
        android:layout_width=\"30dp\" 
        android:layout_height=\"30dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
     
   <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_25\" 
        android:layout_width=\"25dp\" 
        android:layout_height=\"25dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
     
    <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_20\" 
        android:layout_width=\"20dp\" 
        android:layout_height=\"20dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
     
    <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_15\" 
        android:layout_width=\"15dp\" 
        android:layout_height=\"15dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
     
     <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_10\" 
        android:layout_width=\"10dp\" 
        android:layout_height=\"10dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
    <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_5\" 
        android:layout_width=\"5dp\" 
        android:layout_height=\"5dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
     
     <LinearLayout  
      android:layout_width=\"0dp\" 
      android:layout_height=\"match_parent\" 
      android:layout_weight=\"1\" 
      android:gravity=\"center\" 
      > 
      <TextView  
        android:id=\"@+id/tv_2\" 
        android:layout_width=\"2dp\" 
        android:layout_height=\"2dp\" 
        android:background=\"@drawable/bg_notifaction\" 
        /> 
    </LinearLayout> 
  </LinearLayout> 
   
  <picturegame.view.GameView  
    android:layout_width=\"match_parent\" 
    android:layout_height=\"300dp\" 
    android:id=\"@+id/gameview\" 
    /> 
   
       
   
  <Button  
    android:layout_width=\"200dp\" 
    android:layout_height=\"80dp\" 
    android:text=\"clear\" 
    android:textColor=\"@color/black\" 
    android:id=\"@+id/btn_clear\" 
     
    /> 
 
</LinearLayout>

四、主Activity代码

package com.winton.picturegame; 
 
import picturegame.view.GameView; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.TextView; 
 
import com.winton.basemodule.BaseActivity; 
 
public class MainActivity extends BaseActivity implements OnClickListener { 
 
  private GameView gameview = null; 
  private Button clear = null; 
   
  private TextView tv30,tv25,tv20,tv15,tv10,tv5,tv2; 
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
  } 
 
  @Override 
  public void initView() { 
    // TODO Auto-generated method stub 
    setContentView(R.layout.activity_main); 
     
    gameview=(GameView)findViewById(R.id.gameview); 
    clear =(Button)findViewById(R.id.btn_clear); 
    tv30=(TextView)findViewById(R.id.tv_30); 
    tv25=(TextView)findViewById(R.id.tv_25); 
    tv20=(TextView)findViewById(R.id.tv_20); 
    tv15=(TextView)findViewById(R.id.tv_15); 
    tv10=(TextView)findViewById(R.id.tv_10); 
    tv5=(TextView)findViewById(R.id.tv_5); 
    tv2=(TextView)findViewById(R.id.tv_2); 
  } 
 
  @Override 
  public void initListener() { 
    // TODO Auto-generated method stub 
    clear.setOnClickListener(this); 
    tv30.setOnClickListener(this); 
    tv25.setOnClickListener(this); 
    tv20.setOnClickListener(this); 
    tv15.setOnClickListener(this); 
    tv10.setOnClickListener(this); 
    tv5.setOnClickListener(this); 
    tv2.setOnClickListener(this); 
     
  } 
 
  @Override 
  public void initData() { 
    // TODO Auto-generated method stub 
     
  } 
  @Override 
  public void onClick(View v) { 
    // TODO Auto-generated method stub 
    if(v==clear){ 
      gameview.clear(); 
      return; 
    } 
    if(v==tv30){ 
      gameview.setStrokeWidth(30f); 
      return; 
    } 
    if(v==tv25){ 
      gameview.setStrokeWidth(25f); 
      return; 
    } 
    if(v==tv20){ 
      gameview.setStrokeWidth(20f); 
      return; 
    } 
    if(v==tv15){ 
      gameview.setStrokeWidth(15f); 
      return; 
    } 
    if(v==tv10){ 
      gameview.setStrokeWidth(10f); 
      return; 
    } 
    if(v==tv5){ 
      gameview.setStrokeWidth(5f); 
      return; 
    } 
    if(v==tv2){ 
      gameview.setStrokeWidth(2f); 
      return; 
    } 
     
  } 
    
}

五、效果
运行效果图如下

六、疑问
当线条变粗时，线条会出现如上图中不连续的问题。请问高手这个怎么处理呢？我猜测应该要运行算法，但还不知道怎么运行。

文章就为大家介绍到这，其实还有许多知识点小编也不是很清楚，希望大家可以进行补充扩展，共同进步。

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