Android studio编写简单的手电筒APP

package com.example.goo.gfire; import android.app.Activity;import android.hardware.Camera;import android.hardware.Camera.Parameters;import android.os.Bundle;import android.view.View;import android.widget.Button;  public class FireActivity extends Activity {  private Button button;  private Camera camera = Camera.open();  private Parameters parameters;  private boolean islight=true;   public void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_fire);   button = (Button) this.findViewById(R.id.bn);   button.setOnClickListener(new View.OnClickListener() {     @Override     public void onClick(View v) {      if (islight) {        camera.startPreview();        parameters = camera.getParameters();        parameters.setFlashMode(Parameters.FLASH_MODE_TORCH);        camera.setParameters(parameters);        islight = false        ;        button.setText("关");      } else {        parameters = camera.getParameters();        parameters.setFlashMode(Parameters.FLASH_MODE_OFF);        camera.setParameters(parameters);        islight = true;        button.setText("开");      }     }    });  }}

package com.example.goo.gfire; import android.app.Activity;import android.hardware.Camera;import android.hardware.Camera.Parameters;import android.os.Bundle;import android.view.View;import android.widget.Button;  public class FireActivity extends Activity {  private Button button;  private Camera camera = Camera.open();  private Parameters parameters;  private boolean islight=true;   public void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_fire);   button = (Button) this.findViewById(R.id.bn);   button.setOnClickListener(new View.OnClickListener() {     @Override     public void onClick(View v) {      if (islight) {        camera.startPreview();        parameters = camera.getParameters();        parameters.setFlashMode(Parameters.FLASH_MODE_TORCH);        camera.setParameters(parameters);        islight = false        ;        button.setText("关");      } else {        parameters = camera.getParameters();        parameters.setFlashMode(Parameters.FLASH_MODE_OFF);        camera.setParameters(parameters);        islight = true;        button.setText("开");      }     }    });  }}

<?xml version="1.0" encoding="utf-8"?><RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"  android:paddingLeft="@dimen/activity_horizontal_margin"  android:paddingRight="@dimen/activity_horizontal_margin"  android:paddingTop="@dimen/activity_vertical_margin"  app:layout_behavior="@string/appbar_scrolling_view_behavior"  tools:context="com.example.goo.gfire.FireActivity"  tools:showIn="@layout/activity_fire">   <TextView    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:text="电筒模式"    android:textSize="34sp"    android:textStyle="bold"    android:gravity="center"/>  <Button    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:id="@+id/bn"    android:textOff="关"    android:textOn="开"    android:height="400dp"    android:layout_alignParentBottom="true"    android:layout_centerHorizontal="true"    android:layout_marginBottom="59dp"    android:fontFeatureSettings="@string/auth_google_play_services_client_facebook_display_name"    android:textColor="@color/common_signin_btn_dark_text_focused"    android:textStyle="bold"    android:textSize="100sp"    />  </RelativeLayout>