Android_(自动化)自动获取手机电池的剩余电量

package com.example.asus.gary_040a;

import android.app.Dialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.TextView;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity {

    private int intLevel;
    private int intScale;
    private Button mButton01;
    private TextView tv;
    //创建BroadcastReceiver
    private BroadcastReceiver mBatInfoReveiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            //如果捕捉到的Action是ACTION_BATTERY_CHANGED则运行onBatteryInforECEIVER()
            if(intent.ACTION_BATTERY_CHANGED.equals(action))
            {
                //获得当前电量
                intLevel = intent.getIntExtra("level",0);
                //获得手机总电量
                intScale = intent.getIntExtra("scale",100);
                 // 在下面会定义这个函数，显示手机当前电量
                onBatteryInfoReceiver(intLevel, intScale);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mButton01 = (Button) findViewById(R.id.myButton1);
        mButton01.setOnClickListener(new Button.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 注册一个BroadcastReceiver，作为访问电池计量之用
                registerReceiver(mBatInfoReveiver, new IntentFilter(
                        Intent.ACTION_BATTERY_CHANGED));
            }
        });
    }

    // 拦截到ACTION_BATTRY_CHANGED后要执行的动作
    private void onBatteryInfoReceiver(int intLevel, int intScale) {
        // TODO Auto-generated method stub
         int percent = intLevel*100/ intScale;
        //得到的person就是百分比电量
        //不乘100得到的percent为0
        tv=(TextView) findViewById(R.id.myTextView02);
        tv.setText("现在的电量是"+percent+"%。");
    };
}

<?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"
    tools:context="com.example.asus.gary_040a.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Gary_自动获取手机电池的剩余电量!"
        android:textSize="40px"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/myButton1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button" />

    <TextView
        android:id="@+id/myTextView02"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="50px" />

</LinearLayout>