1、倒计时APP

运行图示：**

xml代码

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

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;

}

}