Android实现绘画板功能

一、预期效果二、设置横竖屏切换三、确定布局四、自定义滑动条五、绘画区域六、MainActivity

screenOrientation属性        作用 user 用户当前设置的方向。 unspecified 由系统选择显示方向，不同的设备可能会有所不同。（旋转手机，界面会跟着旋转） landscape 限制界面为横屏，旋转屏幕也不会改变当前状态。 portrait 限制界面为竖屏，旋转屏幕也不会改变当前状态。 behind 与前一个activity方向相同。 sensor 根据传感器定位方向，旋转手机90度，180,270,360，界面都会发生变化。 nosensor 不由传感器确定方向。旋转设备的时候，界面不会跟着旋转。初始界面方向由系统提供。 sensorLandscape （横屏的旋转，不会出现竖屏的现象）根据传感器定位方向，旋转手机180度界面旋转。一般横屏游戏会是这个属性。 sensorPortrait （竖屏的旋转，不会出现横屏的现象）根据传感器定位方向，旋转手机180度界面会旋转。

因为横竖屏切换后控件的宽高都是不一样的，也就是不固定的，不能用线性布局，而是根据相对位置进行布局。先用constraintLayout约束，再将小控件组合成一个线性布局，然后对整个线性布局进行相对布局。

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android='http://schemas.android.com/apk/res/android' xmlns:app='http://schemas.android.com/apk/res-auto' xmlns:tools='http://schemas.android.com/tools' android:layout_width='match_parent' android:layout_height='match_parent' tools:context='.MainActivity'> <androidx.constraintlayout.widget.ConstraintLayoutandroid:layout_width='match_parent'android:layout_height='0dp'app:layout_constraintTop_toTopOf='parent'app:layout_constraintBottom_toTopOf='@id/operation'><!--滑动条--><com.example.a16drawboard.Slider android: android:layout_width='20dp' android:layout_height='match_parent' android:layout_marginLeft='20dp' android:layout_marginTop='20dp' android:layout_marginBottom='20dp' app:layout_constraintLeft_toLeftOf='parent' /><!--画板--><com.example.a16drawboard.DrawBoardView android: android:layout_width='0dp' android:layout_height='match_parent' app:layout_constraintLeft_toRightOf='@id/slider' app:layout_constraintRight_toLeftOf='@id/color'/> <!--选颜色--><LinearLayout android: android:layout_width='60dp' android:layout_height='match_parent' android:orientation='vertical' android:layout_marginRight='20dp' app:layout_constraintRight_toRightOf='parent' android:gravity='center'> <Buttonandroid:layout_width='match_parent'android:layout_height='50dp'android:background='@color/colorAccent'android:onClick='choiceColor'/> <Buttonandroid:layout_width='match_parent'android:layout_height='50dp'android:background='@color/colorPrimary'android:onClick='choiceColor'/> <Buttonandroid:layout_width='match_parent'android:layout_height='50dp'android:background='#f00'android:onClick='choiceColor'/> <Buttonandroid:layout_width='match_parent'android:layout_height='50dp'android:background='#000'android:onClick='choiceColor'/></LinearLayout> </androidx.constraintlayout.widget.ConstraintLayout> <LinearLayoutandroid: android:layout_width='match_parent'android:layout_height='60dp'android:background='#f00'android:orientation='horizontal'app:layout_constraintBottom_toBottomOf='parent'android:gravity='center'><Button android:layout_width='70dp' android:layout_height='wrap_content' android:text='撤销' android:onClick='goBack'/><Button android:layout_width='70dp' android:layout_height='wrap_content' android:text='清空' android:onClick='clear'/><Button android:layout_width='70dp' android:layout_height='wrap_content' android:text='橡皮擦' android:onClick='eraser'/><Button android:layout_width='70dp' android:layout_height='wrap_content' android:text='保存' android:onClick='save'/><Button android:layout_width='70dp' android:layout_height='wrap_content' android:text='上一步' android:onClick='lastStep'/> </LinearLayout></androidx.constraintlayout.widget.ConstraintLayout>四、自定义滑动条

public class Slider extends View { private int lineSize = 6; // 线条的粗细 private int lineColor = Color.BLACK;// 默认线条颜色 private Paint linePaint; private Paint circlePaint; // 圆点画笔 private int thumbColor = Color.MAGENTA; // 圆点颜色 private int cx; // 中心点x private int cy; // 中心点y private int radius; // 小圆点半径 private int thumbScale = 4; // 圆点缩放尺寸 private float position; // 触摸点的坐标 private Paint progressPaint; // 进度条进度的画笔 private int progressColor = Color.MAGENTA; // 进度条颜色 public static int PROGRESS = 0; // 进度条 public static int SLIDER = 1; // 滑动条 private int style = PROGRESS; // 用户选择的样式，默认为进度条 public int max = 100; // 设置最大值 public float progress; // 进度值 private OnSliderChangeListener onSliderChangeListener; // 滑动改变监听者 public Slider(Context context) {super(context); } public Slider(Context context, AttributeSet attrs) {super(context, attrs);init(); } private void init(){// 背景线linePaint = new Paint(Paint.ANTI_ALIAS_FLAG);linePaint.setColor(lineColor);linePaint.setStrokeWidth(lineSize);// 圆点circlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);circlePaint.setColor(thumbColor);circlePaint.setStyle(Paint.Style.FILL);// 进度条progressPaint = new Paint(Paint.ANTI_ALIAS_FLAG);progressPaint.setColor(progressColor);progressPaint.setStrokeWidth(lineSize); } @Override protected void onDraw(Canvas canvas) {if (getWidth() > getHeight()){ // 横着 canvas.drawLine(0, getHeight()/2, getWidth(), getHeight()/2, linePaint); if (position>0){canvas.drawLine(0, getHeight()/2, position, getHeight()/2, progressPaint); } radius = getHeight()/thumbScale; cy = getHeight()/2; // 确定cx的值 if (position < radius) {cx = radius; }else if (position > getWidth()-radius){cx = getWidth()-radius; }else {cx = (int) position; }}else{ // 竖着 canvas.drawLine(getWidth()/2, 0, getWidth()/2, getHeight(), linePaint); if (position>0){canvas.drawLine(getWidth()/2, 0, getWidth()/2, position, progressPaint); } radius = getWidth()/thumbScale; cx = getWidth()/2; // 确定中心点cy的值 if (position<radius){cy = radius; }else if (position > getHeight()-radius){cy = getHeight()-radius; }else {cy = (int) position; }}// 画小圆点if (style == SLIDER){ canvas.drawCircle(cx,cy,radius,circlePaint);} } @Override public boolean onTouchEvent(MotionEvent event) {switch (event.getAction()){ case MotionEvent.ACTION_DOWN:// 圆点放大thumbScale = 2;// 点下去就到那个位置if (getWidth()>getHeight()){ // 横向时，y不变 x改变 position = event.getX();}else { // 纵向时，x不变 y改变 position = event.getY();}callback();break; case MotionEvent.ACTION_MOVE:// 获取当前触摸点的值XYif (getWidth()>getHeight()){ // 横向时，y不变 x改变 position = event.getX(); if (position<0){progress = 0; }else if (position>getWidth()){position = getWidth(); }}else { // 竖着时，x不变 y改变 position = event.getY(); if (position<0){progress = 0; }else if (position>getHeight()){position = getHeight(); }}callback();break; case MotionEvent.ACTION_UP:thumbScale = 4;break;}if (style == SLIDER){ invalidate();}return true; } private void callback(){if (onSliderChangeListener != null){ if (getWidth()>getHeight()){progress = position/getWidth(); }else {progress = position/getHeight(); } onSliderChangeListener.progressChange(progress*max);} } public int getStyle() {return style; } public void setStyle(int style) {this.style = style; } public float getProgress() {return progress; } public void setProgress(int progress){// 计算比例float rate = (float)(progress*1.0/max);setProgress(rate); } public void setProgress(float progress) {this.progress = progress;if (progress <1.001) { // 将进度值转化为控件中的尺寸位置 if (getWidth() > getHeight()) {position = progress * getWidth(); } else {position = progress * getHeight(); } invalidate();} } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) {if (getWidth() > getHeight()) { position = progress * getWidth();} else { position = progress * getHeight();} } public void setMax(int max) {this.max = max; } public interface OnSliderChangeListener{void progressChange(float progress); } public void setOnSliderChangeListener(OnSliderChangeListener onSliderChangeListener) {this.onSliderChangeListener = onSliderChangeListener; }}五、绘画区域

public class DrawBoardView extends View { private ArrayList<Graph> graphs; // 操作数组 private ArrayList<Graph> orginalGraphs; // 原始数组 private int lineColor = Color.BLACK; private int lineSize = 5; Path mPath; public DrawBoardView(Context context) {super(context); } public DrawBoardView(Context context, @Nullable AttributeSet attrs) {super(context, attrs);init(); } private void init(){// 初始化数组graphs = new ArrayList<>();orginalGraphs = new ArrayList<>();setBackgroundColor(Color.WHITE); } @Override protected void onDraw(Canvas canvas) {// 遍历数组Iterator<Graph> iterator = graphs.iterator();while (iterator.hasNext()){ // 从集合中获取一个图形对象 Graph line = iterator.next(); // 绘制图形 canvas.drawPath(line.path,line.paint);} } @Override public boolean onTouchEvent(MotionEvent event) {switch (event.getAction()){ case MotionEvent.ACTION_DOWN:// 创建这条线对应的paint和pathPaint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mPaint.setColor(lineColor);mPaint.setStrokeWidth(lineSize);mPaint.setStyle(Paint.Style.STROKE);mPath = new Path();// 设置图形的起点mPath.moveTo(event.getX(),event.getY());// 保存当前这个图形的详细信息Graph temp = new Graph(mPaint,mPath);graphs.add(temp);orginalGraphs.add(temp);break; case MotionEvent.ACTION_MOVE:// 连接从path终点到当前触摸点的线mPath.lineTo(event.getX(),event.getY());break; case MotionEvent.ACTION_UP:break;}invalidate();return true; } // 用私有类来管理图形的画笔和路径 private class Graph{Paint paint;Path path;public Graph(Paint paint,Path path){ this.paint=paint; this.path=path;} } // 删除最后一个图形 撤销 public void removeLast(){if (graphs.size() >0){ graphs.remove(graphs.size()-1); invalidate();} } // 删除所有 清空 public void removeAll(){graphs.clear();invalidate(); } // 还原上一步 public void returnToLastStep(){// 判断缓存中是否有if (graphs.size() < orginalGraphs.size()){ // 获取上一步的索引值 int index = graphs.size()-1+1; // 从缓存中获取index，添加到操作数组中 graphs.add(orginalGraphs.get(index)); invalidate();} } public int getLineSize() {return lineSize; } public void setLineSize(int lineSize) {this.lineSize = lineSize; } public int getLineColor() {return lineColor; } public void setLineColor(int lineColor) {this.lineColor = lineColor; }}六、MainActivity

public class MainActivity extends AppCompatActivity { private DrawBoardView boardView; @Override protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);// 获取画板对象boardView = findViewById(R.id.board);// 获取滑动条对象final Slider slider = findViewById(R.id.slider);slider.setStyle(Slider.SLIDER);slider.setMax(30);slider.setOnSliderChangeListener(new Slider.OnSliderChangeListener() { @Override public void progressChange(float progress) {boardView.setLineSize((int) progress); }});slider.setProgress(boardView.getLineSize()); } @Override public void onWindowFocusChanged(boolean hasFocus) {super.onWindowFocusChanged(hasFocus); } @Override protected void onStart() {super.onStart(); } @Override protected void onResume() {super.onResume();// 设置横屏setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_FULL_SENSOR); } @Override protected void onPause() {super.onPause(); } @Override protected void onStop() {super.onStop(); } // 选择颜色 获取按钮上面的背景颜色 public void choiceColor(View view) {// 获取按钮上面的背景颜色ColorDrawable drawable = (ColorDrawable) view.getBackground();// 获取颜色boardView.setLineColor(drawable.getColor()); } // 撤回 public void goBack(View view) {boardView.removeLast(); } // 清空 public void clear(View view) {boardView.removeAll(); } // 橡皮擦 public void eraser(View view) {// 获取画板的drawableColorDrawable drawable = (ColorDrawable) boardView.getBackground();// 设置线条颜色和背景色相同if (drawable != null){ boardView.setLineColor(drawable.getColor());}else { boardView.setLineColor(Color.TRANSPARENT);} } // 保存 public void save(View view) { } // 还原 public void lastStep(View view) {boardView.returnToLastStep(); }}

到这里就结束啦。

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