Android 活动会自行刷新，而不是进入预期活动

Question

我在一个活动中有 2 个按钮。一个是注销按钮，可以正常工作，另一个是相机按钮，单击该按钮会导致另一个活动。但是，当我单击相机按钮转到下一个活动（相机功能）时，当前活动只会自行刷新，每次单击它都是额外的时间，我必须单击注销按钮才能注销！（即，如果我单击相机按钮 5 次我必须单击注销按钮 5 次才能注销）。这可能是非常愚蠢的事情，但我是编程新手，所以请耐心等待！这里是相关的代码sn-ps。如果有人可以提供帮助，我将不胜感激。

欢迎课

package com.example.myapp;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import com.parse.ParseUser;

public class Welcome extends Activity {

// Declare Variable
Button logout;
Button cameraButton;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Get the view from singleitemview.xml
    setContentView(R.layout.welcome);  

    // Retrieve current user from Parse.com
    ParseUser currentUser = ParseUser.getCurrentUser();

    // Convert currentUser into String
    String struser = currentUser.getUsername().toString();

    // Locate TextView in welcome.xml
    TextView txtuser = (TextView) findViewById(R.id.txtuser);

    // Set the currentUser String into TextView
    txtuser.setText("You are logged in as " + struser);

    // Locate Button in welcome.xml
    logout = (Button) findViewById(R.id.logout);        

    // Logout Button Click Listener
    logout.setOnClickListener(new OnClickListener() {

        /** Called when the user clicks the Logout button */
        public void onClick(View arg0) {
            // Logout current user
            ParseUser.logOut();
            finish();
     }

 });

 // Locate Button in welcome.xml
    cameraButton = (Button) findViewById(R.id.cameraButton);

    // Camera Button Click Listener
    cameraButton.setOnClickListener(new OnClickListener() {

    /** Called when the user clicks the Camera button */
    public void onClick(View view) {
        // Send user to Camera.class
        Intent intent = new Intent(Welcome.this, Camera.class);
         startActivity(intent);

    }


  });

    }
  }

欢迎 xml 布局文件中的按钮代码

<Button
    android:id="@+id/cameraButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
   android:layout_below="@+id/logout"
    android:layout_centerHorizontal="true"
    android:onClick="sendMessage"
    android:text="@string/CameraBtn" />

清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myapp"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="17"
    android:targetSdkVersion="19" />

<uses-permission android:name="android.permission.INTERNET" />

<application
    android:name="ParseApplication"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name" 
    android:allowBackup="true"
  android:theme="@style/AppTheme" >

    <activity
        android:name="com.example.myapp.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity android:name="com.example.myapp.LoginSignupActivity" >
    </activity>

    <activity android:name="com.example.myapp.Welcome" >
    </activity>

    <activity
        android:name="com.example.myapp.Camera">
    </activity>

</application> 
</manifest>

字符串 xml 文件

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

<string name="hello">myapp</string>
<string name="app_name">myapp</string>
<string name="Username">Username</string>
<string name="Password">Password</string>
<string name="LoginBtn">Login</string>
<string name="SignupBtn">Sign Up</string>
<string name="LogoutBtn">Log Out</string>
 <string name="CameraBtn">Camera</string>
<string name="Welcome">Welcome!</string>  
<string name="tap">Tap the image to open the camera!!</string>
<string name="title_camera">My Message</string> 
</resources>

LoginSignup 类

public class LoginSignupActivity extends Activity {
// Declare Variables
Button loginbutton;
Button signup;
String usernametxt;
String passwordtxt;
EditText password;
EditText username;

/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Get the view from main.xml
    setContentView(R.layout.loginsignup);
    // Locate EditTexts in main.xml
    username = (EditText) findViewById(R.id.username);
    password = (EditText) findViewById(R.id.password);

    // Locate Buttons in main.xml
    loginbutton = (Button) findViewById(R.id.login);
    signup = (Button) findViewById(R.id.signup);

    // Login Button Click Listener
    loginbutton.setOnClickListener(new OnClickListener() {

        public void onClick(View arg0) {
            // Retrieve the text entered from the EditText
            usernametxt = username.getText().toString();
            passwordtxt = password.getText().toString();

            // Send data to Parse.com for verification
            ParseUser.logInInBackground(usernametxt, passwordtxt,
                    new LogInCallback() {
                        public void done(ParseUser user, ParseException e) {
                            if (user != null) {
                                // If user exist and authenticated, send user to       Welcome.class
                                Intent intent = new Intent(
                                        LoginSignupActivity.this,
                                        Welcome.class);
                                startActivity(intent);
                                Toast.makeText(getApplicationContext(),
                                        "Successfully Logged in",
                                        Toast.LENGTH_LONG).show();
                                finish();
                            } else {
                                Toast.makeText(
                                        getApplicationContext(),
                                        "No such user exist, please signup",
                                        Toast.LENGTH_LONG).show();
                            }
                        }
                    });
        }
    });
    // Sign up Button Click Listener
    signup.setOnClickListener(new OnClickListener() {

        public void onClick(View arg0) {
            // Retrieve the text entered from the EditText
            usernametxt = username.getText().toString();
            passwordtxt = password.getText().toString();

            // Force user to fill up the form
            if (usernametxt.equals("") && passwordtxt.equals("")) {
                Toast.makeText(getApplicationContext(),
                        "Please complete the sign up form",
                        Toast.LENGTH_LONG).show();

            } else {
                // Save new user data into Parse.com Data Storage
                ParseUser user = new ParseUser();
                user.setUsername(usernametxt);
                user.setPassword(passwordtxt);
                user.signUpInBackground(new SignUpCallback() {
                    public void done(ParseException e) {
                        if (e == null) {
                            // Show a simple Toast message upon successful registration
                            Toast.makeText(getApplicationContext(),
                                    "Successfully Signed up, please log in.",
                                    Toast.LENGTH_LONG).show();
                        } else {
                            Toast.makeText(getApplicationContext(),
                                    "Sign up Error", Toast.LENGTH_LONG)
                                    .show();
                        }
                    }
                });
            }

        }
    });

  }
 }

ParseUser.logout

 // Locate Button in welcome.xml
    logout = (Button) findViewById(R.id.logout);        

    // Logout Button Click Listener
    logout.setOnClickListener(new OnClickListener() {

        /** Called when the user clicks the Logout button */
        public void onClick(View arg0) {
            // Logout current user
            ParseUser.logOut();
            finish();
     }

});

Answer 1

按钮

<Button
android:id="@+id/cameraButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/logout"
android:layout_centerHorizontal="true"
android:onClick="sendMessage"
android:text="@string/CameraBtn" />

android:onClick="sendMessage" 行表示当单击按钮时，应调用 sendMessage 方法。除非您有 sendMessage 方法，否则我会从您的代码中删除这一行。

意图

/** Called when the user clicks the Camera button */
public void onClick(View view) {
    // Send user to Camera.class
    Intent intent = new Intent(Welcome.this, Camera.class);
     startActivity(intent);

}

new Intent(Welcome.this, Camera.class) 是一种可接受的开始新活动的方式。通过使用Welcome.this 而不是this，您可以正确地获取上下文。

Answer 2

解决了，我在相机类中扩展了 MainActivity 而不是扩展了活动！！

Answer 3

我必须将此作为答案，因为我需要更多的声誉点来发表评论。 一个按钮基本上有两个 onClick 事件，因此您可能需要解决此问题。

android:onClick="sendMessage"

 // Camera Button Click Listener
cameraButton.setOnClickListener(new View.OnClickListener()

而且有时使用 getApplicationContext() 会更好

Intent intent = new Intent(getApplicationContext(), Camera.class);
startActivity(intent)

尝试将您的 onClick 方法修改为以下

// Add a click listener to perform action when button is clicked
         cameraButton.setOnClickListener(
            new View.OnClickListener()
            {
                @Override
                public void onClick( View view )
                {
                }
            });