Android studio 学习3：实现倒计时、画板

1、倒计时APP
运行图示：**
Android studio 学习3：实现倒计时、画板_第1张图片
Android studio 学习3：实现倒计时、画板_第2张图片

xml代码

<?xml version="1.0" encoding="utf-8"?>

java代码

import androidx.annotation.NonNull;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;import java.util.Timer;import java.util.TimerTask;public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private EditText input_time;    private Button getTime,startTime,stopTime;    private TextView time;    private int i = 0;    private Timer timer = null;    private TimerTask task = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate( savedInstanceState );        setContentView( R.layout.activity_main );        initView();    }    private void initView(){        input_time = (EditText) findViewById( R.id.input_time );        getTime = (Button) findViewById( R.id.get_time );        startTime = (Button) findViewById( R.id.start_time );        stopTime = (Button) findViewById( R.id.stop_time );        time = (TextView) findViewById( R.id.time );        getTime.setOnClickListener( this );        stopTime.setOnClickListener( this );        startTime.setOnClickListener( this );    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.get_time:                time.setText( input_time.getText().toString() );                i = Integer.parseInt( input_time.getText().toString() );                break;            case R.id.start_time:                StartTime();                break;            case R.id.stop_time:                StopTime();                break;        }    }    private Handler mHandler = new Handler(){        public void handleMessage(Message msg) {            time.setText(msg.arg1+"");            StartTime();        };    };    public void StartTime(){        timer = new Timer();        task = new TimerTask() {            @Override            public void run() {                i--;                Message message = mHandler.obtainMessage();                message.arg1 = i;                mHandler.sendMessage( message );            }        };        timer.schedule( task, 1000 );    }    public void StopTime(){        timer.cancel();    }}

2、画板APP
xml代码

<?xml version="1.0" encoding="utf-8"?>

java代码1

package com.example.drawingboard;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;public class MainActivity extends AppCompatActivity {    private Button btn;    private MyView view;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate( savedInstanceState );        setContentView( R.layout.activity_main );        btn = (Button)findViewById( R.id.btn );        view = (MyView)findViewById( R.id.draw ) ;        btn.setOnClickListener( new View.OnClickListener() {            @Override            public void onClick(View v) {                view.clear();            }        } );    }}

java代码2

package com.example.drawingboard;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.SurfaceHolder;import android.view.SurfaceView;import android.view.View;public class MyView extends SurfaceView implements SurfaceHolder.Callback, View.OnTouchListener {    private Paint p = new Paint();    private Path path = new Path();    public MyView(Context context, AttributeSet attrs) {        super(context, attrs);        getHolder().addCallback( this );        p.setColor( Color.RED  );        p.setTextSize( 50 );        p.setStyle( Paint.Style.STROKE );//        p.setAntiAlias( true );        setOnTouchListener( this );    }    public void draw(){        Canvas canvas = getHolder().lockCanvas();        canvas.drawColor( Color.WHITE );        canvas.drawPath( path, p );        getHolder().unlockCanvasAndPost( canvas );    }    public void clear(){        path.reset();        draw();    }    @Override    public void surfaceCreated(SurfaceHolder holder) {        draw();    }    @Override    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {    }    @Override    public void surfaceDestroyed(SurfaceHolder holder) {    }    @Override    public boolean onTouch(View v, MotionEvent event) {        switch (event.getAction()){            case MotionEvent.ACTION_DOWN:                path.moveTo( event.getX(),event.getY() );                draw();             break;            case MotionEvent.ACTION_MOVE:                path.lineTo( event.getX(),event.getY() );                draw();             break;        }        return true;    }}

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