Android learning (22)Path "path drawing (to achieve the drawing function)

Path: path, which can be used to draw at will, and can be used to make drawing software

Using Path and SurfaceView to realize drawing function

1. Layout a custom control and a clear button in xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical">
    <com.example.test.androidtest.MyPath
        android:id="@+id/draw"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        >
    </com.example.test.androidtest.MyPath>
    <Button
        android:id="@+id/btnClear"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Clear"/>
</LinearLayout>

2. Implement drawing function in MyPath.java

public class MyPath extends SurfaceView implements SurfaceHolder.Callback,View.OnTouchListener {

    //Declare instantiation path
    private Path path = new Path();
    //Instantiate a brush
    private Paint paint = new Paint();

    public MyPath(Context context) {
        super(context);
    }

    //Load custom control
    public MyPath(Context context, AttributeSet attrs) {
        super(context, attrs);
        //Call initialization operation
        init();
    }

    //Initialize operation
    private void init() {
        //Set touch monitor
        setOnTouchListener(this);
        //Set callback
        getHolder().addCallback(this);
    }

    //Mapping
    public void draw() {
        Canvas canvas = getHolder().lockCanvas();
        canvas.drawColor(0xffffffff);
        canvas.drawPath(path,paint);
        getHolder().unlockCanvasAndPost(canvas);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

    }

    //Call draw method
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        draw();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    //Set touch monitor
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch (event.getAction()) {
            //When the screen is pressed
            case MotionEvent.ACTION_DOWN:
                //Set brush type
                paint.setStyle(Paint.Style.STROKE);
                //Set brush color
                paint.setColor(Color.RED);
                //Get the location of the touch
                path.moveTo(event.getX(),event.getY());
                break;
             //When moving
            case MotionEvent.ACTION_MOVE:
                //Generating lines
                path.lineTo(event.getX(), event.getY());
                //Mapping
                draw();
                break;
        }
        return true;
    }
    //Cleaning canvas
    public void clear(){
        //Reset path
        path.reset();
        draw();
    }
}

3. call in Acticity

public class PathActivity extends AppCompatActivity {

    //Declare a MyPath class
    private MyPath path;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_path);
        //Bring custom controls in
        path = (MyPath)findViewById(R.id.draw);
        //Set clear button monitor
        findViewById(R.id.btnClear).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //Call the clear() function
                path.clear();
            }
        });
    }
}

Statement:
1. The knowledge comes from Netease cloud classroom - Android basic video tutorial
2. This article is only used for my own learning record. If there is any infringement, please inform me to change or delete it immediately