java - 单击按钮使用画布绘制连续线
问题描述
拜托，伙计们，我想通过单击一个按钮在我的 android 项目上画一条连续的线，到目前为止我已经尝试使用 invalidate() 重绘，但是我看到当我调用 invalidate 方法时，而不是保持旧线并从旧线的末端绘制，它重新绘制一条全新的线并擦除旧线。我现在的问题是如何通过单击按钮来保持画线。
下面是我的 MainActivity.java
package com.example.drawlines;
import androidx.appcompat.app.AppCompatActivity;
import androidx.constraintlayout.widget.ConstraintLayout;
import androidx.constraintlayout.widget.ConstraintSet;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.RelativeLayout;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
LinearLayout device;
LinearLayout UIControls;
LinearLayout UIControls1;
LinearLayout UIControls2;
LinearLayout UIControls3;
RelativeLayout UILast;
TextView lineThick, lineColor, arrowKeys;
Spinner lineThickness;
RadioGroup rgb_Group;
RadioButton red, yellow, cyan;
public static int startX;
public static int startY;
public static int endX = 0;
public static int endY = 0;
Button clear, reset;
ImageButton up, down, left, right;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
device = new LinearLayout(this);
LinearLayout.LayoutParams deviceParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.MATCH_PARENT);
device.setLayoutParams(deviceParameters);
device.setOrientation(LinearLayout.VERTICAL);
UIControls = new LinearLayout(this);
LinearLayout.LayoutParams UIControlsParameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);
UIControls.setLayoutParams(UIControlsParameters);
UIControls.setOrientation(LinearLayout.HORIZONTAL);
LinearLayout.LayoutParams UIControls1ParametersAlign = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT,1.0f);
/**clear = new Button(this);
clear.setText("Clear");
clear.setLayoutParams(UIControls1ParametersAlign);
reset = new Button(this);
reset.setText("Reset");
reset.setLayoutParams(UIControls1ParametersAlign);**/
UIControls1 = new LinearLayout(this);
LinearLayout.LayoutParams UIControls1Parameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT, 1.0f);
UIControls1.setLayoutParams(UIControls1Parameters);
UIControls1.setOrientation(LinearLayout.VERTICAL);
lineThick = new TextView(this);
lineThick.setText("Line Thickness");
List<Integer> thicknessDigits = new ArrayList<Integer>();
thicknessDigits.add(10);
thicknessDigits.add(20);
thicknessDigits.add(30);
thicknessDigits.add(40);
thicknessDigits.add(50);
ArrayAdapter<Integer> thicknessAdapter = new ArrayAdapter<Integer>(
this,android.R.layout.simple_spinner_dropdown_item,thicknessDigits
);
lineThickness = new Spinner(this);
//lineThickness.setScrollBarSize(6);
lineThickness.setAdapter(thicknessAdapter);
LinearLayout.LayoutParams spinnerSize = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
lineThickness.setLayoutParams(spinnerSize);
lineThick.setLayoutParams(spinnerSize);
UIControls1.addView(lineThick);
UIControls1.addView(lineThickness);
UIControls1.setBackgroundColor(Color.RED);
//UIControls1.addView(clear);
//UIControls1.addView(reset);
UIControls2 = new LinearLayout(this);
LinearLayout.LayoutParams UIControls2Parameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT,1.0f);
UIControls2.setLayoutParams(UIControls2Parameters);
UIControls2.setOrientation(LinearLayout.VERTICAL);
lineColor = new TextView(this);
lineColor.setText("Line Color");
lineColor.setLayoutParams(UIControls1ParametersAlign);
rgb_Group = new RadioGroup(this);
rgb_Group.setOrientation(LinearLayout.VERTICAL);
red = new RadioButton(this);
red.setText("Red");
rgb_Group.addView(red);
yellow = new RadioButton(this);
yellow.setText("Yellow");
rgb_Group.addView(yellow);
cyan = new RadioButton(this);
cyan.setText("Cyan");
rgb_Group.addView(cyan);
rgb_Group.setLayoutParams(UIControls1ParametersAlign);
UIControls2.addView(lineColor);
UIControls2.addView(rgb_Group);
UIControls2.setBackgroundColor(Color.GREEN);
UIControls3 = new LinearLayout(this);
LinearLayout.LayoutParams UIControls3Parameters = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.MATCH_PARENT,1.0f);
UIControls3.setLayoutParams(UIControls3Parameters);
UIControls3.setOrientation(LinearLayout.VERTICAL);
arrowKeys = new TextView(this);
arrowKeys.setText("Arrow Keys");
UIControls3.addView(arrowKeys);
UIControls3.setBackgroundColor(Color.RED);
UILast = new RelativeLayout(this);
RelativeLayout.LayoutParams relativeAlign = new RelativeLayout.LayoutParams(350,ViewGroup.LayoutParams.MATCH_PARENT);
RelativeLayout.LayoutParams arrowAlign = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
RelativeLayout.LayoutParams arrowAlignRight = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
RelativeLayout.LayoutParams arrowAlignLeft = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
RelativeLayout.LayoutParams arrowAlignDown = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT);
UILast.setLayoutParams(relativeAlign);
UILast.setBackgroundColor(Color.BLUE);
/**arrowKeys = new TextView(this);
arrowKeys.setText("Arrow Keys");
arrowKeys.setLayoutParams(arrowAlign);
UILast.addView(arrowKeys);
clear = new Button(this);
clear.setText("^");
clear.setLayoutParams(arrowAlign);**/
//arrowAlign.width = 50;
arrowAlign.addRule(RelativeLayout.CENTER_HORIZONTAL);
DrawerApp.upp = new ImageButton(this);
DrawerApp.upp.setImageResource(R.drawable.up18);
DrawerApp.upp.setBackgroundColor(Color.WHITE);
DrawerApp.upp.setPadding(20,20,20,20);
DrawerApp.upp.setLayoutParams(arrowAlign);
UILast.addView(DrawerApp.upp);
arrowAlignDown.addRule(RelativeLayout.CENTER_HORIZONTAL);
arrowAlignDown.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
DrawerApp.downn = new ImageButton(this);
DrawerApp.downn.setImageResource(R.drawable.down18);
DrawerApp.downn.setBackgroundColor(Color.WHITE);
DrawerApp.downn.setPadding(20,20,20,20);
DrawerApp.downn.setLayoutParams(arrowAlignDown);
UILast.addView(DrawerApp.downn);
/**arrowAlignRight.addRule(RelativeLayout.CENTER_IN_PARENT);
arrowAlignRight.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
right = new ImageButton(this);
right.setImageResource(R.drawable.right18);
right.setBackgroundColor(Color.WHITE);
right.setPadding(20,20,20,20);
right.setLayoutParams(arrowAlignRight);
UILast.addView(right);**/
arrowAlignRight.addRule(RelativeLayout.CENTER_IN_PARENT);
arrowAlignRight.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
right = new ImageButton(this);
right.setImageResource(R.drawable.right18);
right.setBackgroundColor(Color.WHITE);
right.setPadding(20,20,20,20);
right.setLayoutParams(arrowAlignRight);
UILast.addView(right);
arrowAlignLeft.addRule(RelativeLayout.CENTER_IN_PARENT);
arrowAlignLeft.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
left = new ImageButton(this);
left.setImageResource(R.drawable.left18);
left.setBackgroundColor(Color.WHITE);
left.setPadding(20,20,20,20);
left.setLayoutParams(arrowAlignLeft);
UILast.addView(left);
/**
arrowAlignRight.addRule(RelativeLayout.CENTER_IN_PARENT);
arrowAlignRight.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
right = new ImageButton(this);
right.setImageResource(R.drawable.right18);
right.setBackgroundColor(Color.WHITE);
right.setPadding(20,20,20,20);
right.setLayoutParams(arrowAlignRight);
UILast.addView(right);
**/
UIControls3.addView(UILast);
clear = new Button(this);
clear.setText("Clear Canvas");
clear.setLayoutParams(spinnerSize);
UIControls.addView(UIControls1);
UIControls.addView(UIControls2);
UIControls.addView(UIControls3);
device.addView(UIControls);
device.addView(clear);
device.addView(new DrawerApp(this));
setContentView(device);
}
}
这是我的 DrawerApp.java 类
package com.example.drawlines;
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.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.Toast;
import androidx.annotation.Nullable;
public class DrawerApp extends View {
public int startX = 0;
public int startY = 0;
public int enderX = 0;
public int enderY = 0;
public static ImageButton upp;
public static ImageButton downn;
public Canvas can;
Paint paint;
Path linePath = new Path();
public DrawerApp(final Context context) {
super(context);
paint = new Paint();
paint.setColor(Color.RED);
paint.setStrokeWidth(8);
paint.setStyle(Paint.Style.STROKE);
setBackgroundColor(Color.BLUE);
//setOrientation(HORIZONTAL);
//Button clear = new Button(context);
upp.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
String str = "Up Clicked";
Toast.makeText(context.getApplicationContext(),str, Toast.LENGTH_SHORT).show();
startX = enderX;
startY = enderY;
enderX += 130;
enderY += 120;
invalidate();
//startX = enderX;
//startY = enderY;
}
});
downn.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
String str = "Down Clicked";
Toast.makeText(context.getApplicationContext(),str, Toast.LENGTH_SHORT).show();
startX = enderX;
startY = enderY;
enderX += 20;
enderY += 98;
invalidate();
//drawLine(enderX, enderY);
}
});
}
public void drawLine(int endx, int endy)
{
startX = enderX;
startY = enderY;
}
public void draw()
{
can.drawLine(10,30,120,400, paint);
}
@Override
protected void onDraw(Canvas canvas) {
//Paint paint =
//Drawing a Line (StartX, StartY, EndX, EndY, PaintObj)
canvas.drawLine(startX,startY,enderX,enderY, paint);
//linePath.reset();
//linePath.moveTo(0,0);
//linePath.lineTo(120, 200);
//canvas.drawPath(linePath, paint);
//canvas.drawLine(0,0,120,120, paint);
//invalidate();
}
}
当我运行我的代码时，它看起来像下面
当我单击向上箭头时，它会从中创建一个新行并删除旧行
但下面实际上是我想要实现的。
解决方案
推荐阅读
- python - 如何从 pandas DataFrame 输出包含合并单元格的 html 表
- jquery - 如何实现引导日期时间选择器以具有日历字段
- c# - 与 Epson FP-81 II（财务打印机）的错误通信
- user-interface - AlertDialog 的子容器不覆盖宽度
- flutter - 在 Flutter 中使用 pushNamed 导航后如何使 OverlayEntry 消失
- python - 从 Python 中的目录转换所有文件（.jpg 到 .png）
- firebase - 为什么“无法再从 http 页面调用方法 FB.login。” 是否出现在我的 Ionic4 应用程序中？
- java - 我们可以动态添加带有 setter 和 getter 的类属性吗
- haskell - Haskell：理解绑定和 >> 函数
- python - 编解码器无法解码字节 0x81