02 自定义手写签名控件

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手写签名

自定义 View
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import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import java.util.LinkedList;
public class PaintView extends View {
    /**
     * 存储所有的线条
     */
    private LinkedList<LinkedList<FPoint>> mLines;
    /**
     * 存储撤回的线条
     */
    private LinkedList<LinkedList<FPoint>> mRecyles;
    private Paint mPaintLine;
    private boolean isTouching;
    public PaintView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // 设定画笔
        mPaintLine = new Paint();
        mPaintLine.setColor(Color.GREEN);
        mPaintLine.setStrokeWidth(4);
        // 建构线条数据结构对象
        mLines = new LinkedList<>();
        mRecyles = new LinkedList<>();
    }
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_UP) {
            // 离开屏幕
            isTouching = false;
        } else {
            LinkedList<FPoint> line;
            // 触摸开始
            if (!isTouching) {
                line = new LinkedList<>();
                mLines.add(line);
                isTouching = true;
            } else {
                // 开始滑动
                line = mLines.getLast();
            }
            line.add(new FPoint(event.getX(), event.getY()));
            postInvalidate();
        }
        return true;
    }
    @Override
    protected void onDraw(Canvas canvas) {
        for (LinkedList<FPoint> line : mLines) {
            if (line.size() > 1) {
                // 至少两个点才能画一条线
                for (int i = 1; i < line.size(); i++) {
                    FPoint p1 = line.get(i - 1);
                    FPoint p2 = line.get(i);
                    canvas.drawLine(p1.x, p1.y, p2.x, p2.y, mPaintLine);
                }
            }
        }
    }
    public void clear() {
        if (mLines != null) {
            mLines.clear();
            postInvalidate();
        }
    }
    public void undo() {
        if (mLines != null && mLines.size() > 0 && mRecyles != null) {
            mRecyles.add(mLines.removeLast());
            postInvalidate();
        }
    }
    public void redo() {
        if (mRecyles != null && mRecyles.size() > 0 && mLines != null) {
            mLines.add(mRecyles.removeLast());
            postInvalidate();
        }
    }
    private class FPoint {
        private float x, y;
        private FPoint(float x, float y) {
            this.x = x;
            this.y = y;
        }
    }
}
界面操作代码
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public class DemoActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.act_demo);
        final PaintView paintView = findViewById(R.id.paint_view);
        findViewById(R.id.clear).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                paintView.clear();
            }
        });
        findViewById(R.id.undo).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                paintView.undo();
            }
        });
        findViewById(R.id.redo).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                paintView.redo();
            }
        });
    }
}
界面布局
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<?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:background="#FFF"
    android:orientation="vertical">
    <com.xxt.xtest.PaintView
        android:id="@+id/paint_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:orientation="horizontal">
        <Button
            android:id="@+id/clear"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            android:text="Clear"/>
        <Button
            android:id="@+id/undo"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            android:text="Undo"/>
        <Button
            android:id="@+id/redo"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            android:text="Redo"/>
    </LinearLayout>
</LinearLayout>