在Android studio环境下提供一个完整的实现画板功能的程序

好的，以下是一个简单的Android画板应用程序的实现代码，你可以根据自己的需求进行修改和扩展：

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical">

   <FrameLayout
       android:id="@+id/frame_layout"
       android:layout_width="match_parent"
       android:layout_height="0dp"
       android:layout_weight="1" />

   <LinearLayout
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:orientation="horizontal"
       android:padding="16dp">

       <Button
           android:id="@+id/btn_color"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="1"
           android:text="Color" />

       <Button
           android:id="@+id/btn_brush"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="1"
           android:text="Brush" />

       <Button
           android:id="@+id/btn_clear"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="1"
           android:text="Clear" />

   </LinearLayout>

</LinearLayout>

MainActivity.java:

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

   private Button btnColor, btnBrush, btnClear;
   private FrameLayout frameLayout;
   private DrawingView drawingView;

   private int selectedColor = Color.BLACK;
   private int selectedBrushSize = 10;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);

       btnColor = findViewById(R.id.btn_color);
       btnBrush = findViewById(R.id.btn_brush);
       btnClear = findViewById(R.id.btn_clear);
       frameLayout = findViewById(R.id.frame_layout);

       drawingView = new DrawingView(this);
       frameLayout.addView(drawingView);

       btnColor.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               ColorPickerDialog colorPickerDialog = new ColorPickerDialog(MainActivity.this, selectedColor, new ColorPickerDialog.OnColorChangedListener() {
                   @Override
                   public void colorChanged(int color) {
                       selectedColor = color;
                   }
               });
               colorPickerDialog.show();
           }
       });

       btnBrush.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               BrushSizeDialog brushSizeDialog = new BrushSizeDialog(MainActivity.this, selectedBrushSize, new BrushSizeDialog.OnBrushSizeChangedListener() {
                   @Override
                   public void brushSizeChanged(int brushSize) {
                       selectedBrushSize = brushSize;
                   }
               });
               brushSizeDialog.show();
           }
       });

       btnClear.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               drawingView.clearCanvas();
           }
       });
   }

   public class DrawingView extends View {

       private Paint paint;
       private Path path;

       public DrawingView(Context context) {
           super(context);
           init();
       }

       public DrawingView(Context context, AttributeSet attrs) {
           super(context, attrs);
           init();
       }

       public DrawingView(Context context, AttributeSet attrs, int defStyleAttr) {
           super(context, attrs, defStyleAttr);
           init();
       }

       private void init() {
           paint = new Paint();
           paint.setAntiAlias(true);
           paint.setColor(selectedColor);
           paint.setStyle(Paint.Style.STROKE);
           paint.setStrokeJoin(Paint.Join.ROUND);
           paint.setStrokeCap(Paint.Cap.ROUND);
           paint.setStrokeWidth(selectedBrushSize);

           path = new Path();
       }

       public void clearCanvas() {
           path.reset();
           invalidate();
       }

       @Override
       protected void onDraw(Canvas canvas) {
           super.onDraw(canvas);
           canvas.drawPath(path, paint);
       }

       @Override
       public boolean onTouchEvent(MotionEvent event) {
           switch (event.getAction()) {
               case MotionEvent.ACTION_DOWN:
                   path.moveTo(event.getX(), event.getY());
                   return true;

               case MotionEvent.ACTION_MOVE:
                   path.lineTo(event.getX(), event.getY());
                   invalidate();
                   return true;

               case MotionEvent.ACTION_UP:
                   return true;

               default:
                   return false;
           }
       }
   }
}

ColorPickerDialog.java:

import android.app.Dialog;
import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;

public class ColorPickerDialog extends Dialog {

   private int initialColor;
   private OnColorChangedListener onColorChangedListener;

   public ColorPickerDialog(Context context, int initialColor, OnColorChangedListener onColorChangedListener) {
       super(context);
       this.initialColor = initialColor;
       this.onColorChangedListener = onColorChangedListener;
   }

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.dialog_color_picker);

       final SeekBar seekBarRed = findViewById(R.id.seek_bar_red);
       final SeekBar seekBarGreen = findViewById(R.id.seek_bar_green);
       final SeekBar seekBarBlue = findViewById(R.id.seek_bar_blue);
       final View colorView = findViewById(R.id.color_view);
       Button btnOk = findViewById(R.id.btn_ok);

       final int red = Color.red(initialColor);
       final int green = Color.green(initialColor);
       final int blue = Color.blue(initialColor);

       seekBarRed.setProgress(red);
       seekBarGreen.setProgress(green);
       seekBarBlue.setProgress(blue);
       colorView.setBackgroundColor(initialColor);

       seekBarRed.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
           @Override
           public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
               colorView.setBackgroundColor(Color.rgb(progress, green, blue));
           }

           @Override
           public void onStartTrackingTouch(SeekBar seekBar) {

           }

           @Override
           public void onStopTrackingTouch(SeekBar seekBar) {

           }
       });

       seekBarGreen.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
           @Override
           public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
               colorView.setBackgroundColor(Color.rgb(red, progress, blue));
           }

           @Override
           public void onStartTrackingTouch(SeekBar seekBar) {

           }

           @Override
           public void onStopTrackingTouch(SeekBar seekBar) {

           }
       });

       seekBarBlue.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
           @Override
           public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
               colorView.setBackgroundColor(Color.rgb(red, green, progress));
           }

           @Override
           public void onStartTrackingTouch(SeekBar seekBar) {

           }

           @Override
           public void onStopTrackingTouch(SeekBar seekBar) {

           }
       });

       btnOk.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               int color = Color.rgb(seekBarRed.getProgress(), seekBarGreen.getProgress(), seekBarBlue.getProgress());
               onColorChangedListener.colorChanged(color);
               dismiss();
           }
       });
   }

   public interface OnColorChangedListener {
       void colorChanged(int color);
   }
}

BrushSizeDialog.java:

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;

public class BrushSizeDialog extends Dialog {

   private int initialBrushSize;
   private OnBrushSizeChangedListener onBrushSizeChangedListener;

   public BrushSizeDialog(Context context, int initialBrushSize, OnBrushSizeChangedListener onBrushSizeChangedListener) {
       super(context);
       this.initialBrushSize = initialBrushSize;
       this.onBrushSizeChangedListener = onBrushSizeChangedListener;
   }

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.dialog_brush_size);

       final TextView txtBrushSize = findViewById(R.id.txt_brush_size);
       final SeekBar seekBarBrushSize = findViewById(R.id.seek_bar_brush_size);
       Button btnOk = findViewById(R.id.btn_ok);

       txtBrushSize.setText(String.valueOf(initialBrushSize));
       seekBarBrushSize.setProgress(initialBrushSize);

       seekBarBrushSize.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
           @Override
           public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
               txtBrushSize.setText(String.valueOf(progress));
           }

           @Override
           public void onStartTrackingTouch(SeekBar seekBar) {

           }

           @Override
           public void onStopTrackingTouch(SeekBar seekBar) {

           }
       });

       btnOk.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               int brushSize = seekBarBrushSize.getProgress();
               onBrushSizeChangedListener.brushSizeChanged(brushSize);
               dismiss();
           }
       });
   }

   public interface OnBrushSizeChangedListener {
       void brushSizeChanged(int brushSize);
   }
}

这个画板应用程序实现了以下功能：

- 可以选择不同的画笔颜色；
- 可以选择不同的画笔大小；
- 可以清除画板。

你可以根据自己的需求进行修改和扩展，添加更多的功能。