java - 如何在Android中使用CanvasView显示按钮？

我使用CanvasView在其上放置图像。在CanvasView之后，我在布局文件上放置了一些按钮。

这是我的CanvasView代码，

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;

/**
 * Created by user on 4/28/2016.
 */
public class CanvasView extends View {

    public int width;
    public int height;
    private Bitmap mBitmap;
    private Canvas mCanvas;
    private Path mPath;
    Context context;
    private Paint mPaint;
    private float mX, mY;
    private static final float TOLERANCE = 5;

    public CanvasView(Context c, AttributeSet attrs) {
        super(c, attrs);
        context = c;

        mPath = new Path();

        mPaint = new Paint();
        mPaint.setStrokeWidth(3);
        mPaint.setColor(Color.CYAN);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        // your Canvas will draw onto the defined Bitmap
        mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
    }

    // override onDraw
    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);

        Drawable d = getResources().getDrawable(R.drawable.circle_1);

        int canvasHeight= mCanvas.getHeight();
        int canvasWidth= mCanvas.getWidth();

        Log.d("Height - "," / "+mCanvas.getHeight());
        Log.d("Width - "," / "+mCanvas.getWidth());

//         DisplayMetrics displaymetrics = new DisplayMetrics();
//        ((Activity)context).getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
//        int height = displaymetrics.heightPixels;
//        int width = displaymetrics.widthPixels;

        float h=canvasHeight/2;
        float w=canvasWidth/2;
        float r=canvasWidth/2;

        d.setBounds(0, 0, canvasWidth, (canvasHeight / 8) * 5);
        d.draw(canvas);

       // canvas.drawCircle(w, h, r, mPaint);
    }

}

这是我的布局文件，

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

    <com.example.co.CanvasView
        android:id="@+id/signature_canvas"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true" />

    <LinearLayout
        android:id="@+id/llParent"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/signature_canvas"
        android:layout_marginTop="50dp"
        android:orientation="horizontal">

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="1"
            android:id="@+id/step18button1"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:background="@drawable/button_border"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="2"
            android:id="@+id/step18button2"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignTop="@+id/step18button1"
            android:layout_toRightOf="@+id/step18button1"
            android:layout_toEndOf="@+id/step18button1"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="3"
            android:id="@+id/step18button3"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button2"
            android:layout_toRightOf="@+id/step18button2"
            android:layout_toEndOf="@+id/step18button2"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="4"
            android:id="@+id/step18button4"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button3"
            android:layout_toRightOf="@+id/step18button3"
            android:layout_toEndOf="@+id/step18button3"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="5"
            android:id="@+id/step18button5"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button4"
            android:layout_toRightOf="@+id/step18button4"
            android:layout_toEndOf="@+id/step18button4"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="6"
            android:id="@+id/step18button6"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button5"
            android:layout_toRightOf="@+id/step18button5"
            android:layout_toEndOf="@+id/step18button5"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="7"
            android:id="@+id/step18button7"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button6"
            android:layout_toRightOf="@+id/step18button6"
            android:layout_toEndOf="@+id/step18button6"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="8"
            android:id="@+id/step18button8"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button7"
            android:layout_toRightOf="@+id/step18button7"
            android:layout_toEndOf="@+id/step18button7"
            android:background="@drawable/button_border"/>

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="39dp"
            android:layout_height="wrap_content"
            android:text="9"
            android:id="@+id/step18button9"
            android:textSize="13dp"
            android:layout_marginLeft="3dp"
            android:layout_weight="1"
            android:layout_alignBottom="@+id/step18button8"
            android:layout_toRightOf="@+id/step18button8"
            android:layout_toEndOf="@+id/step18button8"
            android:background="@drawable/button_border"/>
    </LinearLayout>

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:id="@+id/step18editText"
        android:paddingLeft="10dp"
        android:layout_below="@+id/llParent"
        android:layout_alignLeft="@+id/llParent"
        android:layout_alignStart="@+id/llParent"
        android:layout_marginTop="20dp" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:id="@+id/step18editText2"
        android:layout_alignTop="@+id/step18editText"
        android:layout_centerHorizontal="true" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:id="@+id/step18editText3"
        android:paddingRight="10dp"
        android:layout_alignTop="@+id/step18editText2"
        android:layout_alignRight="@+id/step18textView5"
        android:layout_alignEnd="@+id/step18textView5"
        android:layout_marginRight="5dp"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/content25"
        android:id="@+id/step18textView2"
        android:textAlignment="textStart"
        android:textSize="18dp"
        android:paddingLeft="10dp"
        android:layout_alignTop="@+id/step18textView4"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/content26"
        android:id="@+id/step18textView4"
        android:textSize="18dp"
        android:textAlignment="center"
        android:layout_alignTop="@+id/step18textView5"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/content27"
        android:id="@+id/step18textView5"
        android:textSize="18dp"
        android:textAlignment="textEnd"
        android:paddingRight="10dp"
        android:layout_below="@+id/step18editText3"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

</RelativeLayout>

这就是我用CanvasView创建图像的方式，

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

/**
 * Created by user on 5/23/2016.
 */
public class StepTwentyOneFragment extends Fragment {

    private CanvasView customCanvas;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.step21_fragment, container, false);
        customCanvas=(CanvasView)v.findViewById(R.id.signature_canvas);

        return v;
    }

    public static StepTwentyOneFragment newInstance() {

        StepTwentyOneFragment f = new StepTwentyOneFragment();
        Bundle b = new Bundle();

        f.setArguments(b);

        return f;
    }


    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if(isVisibleToUser) {
            Activity a = getActivity();
            if(a != null) a.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        }
    }

}

启动此应用程序时，我看不到CanvasView下方的按钮。现在我的问题是，为什么我看不到按钮？

以及如何减小CanvasView的高度以查看按钮？

最佳答案

您将CanvasView设置为android:layout_height="match_parent"，而LinearLayout android:layout_below="@+id/signature_canvas"。因此CanvasView覆盖整个屏幕，而LinearLayout在屏幕下方位于其下方。

只需将CanvasView更改为wrap_content或某个固定高度即可，具体取决于您的设计需求。