- html - 出于某种原因,IE8 对我的 Sass 文件中继承的 html5 CSS 不友好?
- JMeter 在响应断言中使用 span 标签的问题
- html - 在 :hover and :active? 上具有不同效果的 CSS 动画
- html - 相对于居中的 html 内容固定的 CSS 重复背景?
我想知道是否有人可以帮忙。每次我运行我的 Android 应用程序项目时它都会崩溃。我已将其范围缩小到一个函数,但我不知道为什么它会崩溃!
错误:
05-07 17:38:22.059 3952-3986/com.tfs.appname W/System: ClassLoader referenced unknown path: /data/data/com.tfs.appname/lib
05-07 17:38:22.122 3952-3952/com.tfs.appname D/AndroidRuntime: Shutting down VM
05-07 17:38:22.123 3952-3952/com.tfs.appname E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tfs.appname, PID: 3952
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tfs.appname/com.tfs.appname.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4077)
at android.app.ActivityThread.-wrap15(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1350)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
at android.content.ContextWrapper.getPackageName(ContextWrapper.java:133)
at android.app.Activity.getLocalClassName(Activity.java:5205)
at android.app.Activity.getPreferences(Activity.java:5239)
at com.tfs.appname.helpers.isLoggedIn(helpers.java:99)
at com.tfs.appname.MainActivity$override.onCreate(MainActivity.java:35)
at com.tfs.appname.MainActivity$override.access$dispatch(MainActivity.java)
at com.tfs.appname.MainActivity.onCreate(MainActivity.java:0)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4077)
at android.app.ActivityThread.-wrap15(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1350)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
05-07 17:38:30.716 3952-3952/com.tfs.appname I/Process: Sending signal. PID: 3952 SIG: 9
MainActivity.java:
package com.tfs.appname;
import android.content.Intent;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;
public class MainActivity extends AppCompatActivity {
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
Button LoginButton, RegisterButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final helpers helpers = new helpers();
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
Button LoginButton = (Button) findViewById(R.id.button_login);
Button RegisterButton = (Button) findViewById(R.id.button_register);
if (helpers.isLoggedIn()) {
startActivity(new Intent(MainActivity.this, Dashboard.class));
}
RegisterButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(MainActivity.this, Register.class));
}
});
LoginButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(MainActivity.this, Login.class));
}
});
}
@Override
public void onStart() {
super.onStart();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client.connect();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Main Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.tfs.appname/http/host/path")
);
AppIndex.AppIndexApi.start(client, viewAction);
}
@Override
public void onStop() {
super.onStop();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Main Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.tfs.appname/http/host/path")
);
AppIndex.AppIndexApi.end(client, viewAction);
client.disconnect();
}
}
登录.Java:
package com.tfs.appname;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;
import com.kosalgeek.asynctask.AsyncResponse;
import com.kosalgeek.asynctask.PostResponseAsyncTask;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.HashMap;
import static android.app.PendingIntent.getActivity;
public class Login extends AppCompatActivity implements AsyncResponse {
Button LoginSubmitButton, LoginRegisterButton;
EditText LoginEmail, LoginPassword;
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
final helpers helpers = new helpers();
final EditText LoginEmail = (EditText) findViewById(R.id.login_email);
final EditText LoginPassword = (EditText) findViewById(R.id.login_password);
Button LoginSubmitButton = (Button) findViewById(R.id.login_submit);
Button LoginRegisterButton = (Button) findViewById(R.id.login_register_button);
LoginRegisterButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(Login.this, Register.class));
}
});
assert LoginSubmitButton != null;
LoginSubmitButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
final Context context = getApplicationContext();
int duration = Toast.LENGTH_SHORT;
if (helpers.isEmpty(LoginEmail)) {
CharSequence text = "Please enter your email address.";
Toast toast = Toast.makeText(context, text, duration);
toast.show();
} else {
if (helpers.isEmpty(LoginPassword)) {
CharSequence text = "Please enter your password.";
Toast toast = Toast.makeText(context, text, duration);
toast.show();
} else {
if (helpers.isValidEmail(LoginEmail))
if (helpers.isValidPassword(LoginPassword)) {
HashMap<String, String> postData = new HashMap<String, String>();
postData.put("emailaddress", LoginEmail.getText().toString());
postData.put("password", LoginPassword.getText().toString());
final PostResponseAsyncTask loginTask = new PostResponseAsyncTask(Login.this, postData, new AsyncResponse() {
@Override
public void processFinish(String s) {
JSONObject results = null;
String result_status = null;
String MID = null;
String MT = null;
try {
results = new JSONObject(s);
result_status = results.getString("STATUS");
MID = results.getString("MID");
MT = results.getString("MT");
} catch (JSONException e) {
e.printStackTrace();
}
if (result_status.equalsIgnoreCase("success")) {
SharedPreferences sharedPref = Login.this.getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("MID", MID);
editor.putString("MTOK", MT);
editor.commit();
startActivity(new Intent(Login.this, Dashboard.class));
} else {
Context context = getApplicationContext();
int duration = Toast.LENGTH_SHORT;
CharSequence text = result_status;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
}
}
});
loginTask.execute("http://192.168.1.64/app/test.php");
} else {
CharSequence text = "Invalid password.";
Toast toast = Toast.makeText(context, text, duration);
toast.show();
}
else {
CharSequence text = "Invalid email address.";
Toast toast = Toast.makeText(context, text, duration);
toast.show();
}
}
}
}
});
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}
@Override
public void processFinish(String s) {
}
@Override
public void onStart() {
super.onStart();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client.connect();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Login Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.tfs.appname/http/host/path")
);
AppIndex.AppIndexApi.start(client, viewAction);
}
@Override
public void onStop() {
super.onStop();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Login Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.tfs.appname/http/host/path")
);
AppIndex.AppIndexApi.end(client, viewAction);
client.disconnect();
}
}
Helpers.Java:
package com.tfs.appname;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.util.Patterns;
import android.widget.EditText;
import android.widget.Toast;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;
import com.kosalgeek.asynctask.AsyncResponse;
import com.kosalgeek.asynctask.PostResponseAsyncTask;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Created by Offic on 03/05/2016.
*/
public class helpers extends AppCompatActivity implements AsyncResponse {
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
boolean isEmpty(EditText etText) {
return etText.getText().toString().trim().length() <= 0;
}
public boolean isValidEmail(EditText email) {
if (TextUtils.isEmpty(email.getText())) {
return false;
} else {
return Patterns.EMAIL_ADDRESS.matcher(email.getText()).matches();
}
}
public boolean isValidPassword(EditText password) {
String regExpn = "^[a-z0-9_]{6,24}$";
CharSequence inputStr = password.getText();
Pattern pattern = Pattern.compile(regExpn, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(inputStr);
if (matcher.matches()) {
return true;
} else {
return false;
}
}
private boolean verifySession(String MID, String MTOK) {
HashMap<String, String> postData = new HashMap<String, String>();
postData.put("MID", MID);
postData.put("MTOK", MTOK);
final Boolean[] Ret = {false};
final PostResponseAsyncTask loginTask = new PostResponseAsyncTask(this, postData, new AsyncResponse() {
@Override
public void processFinish(String s) {
JSONObject results = null;
String result_status = null;
try {
results = new JSONObject(s);
result_status = results.getString("STATUS");
} catch (JSONException e) {
e.printStackTrace();
}
if (result_status == "success") {
Ret[0] = true;
} else {
Ret[0] = false;
}
}
});
loginTask.execute("http://192.168.1.64/app/test.php");
return Ret[0];
}
public boolean isLoggedIn() {
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
String MID = sharedPref.getString("MID", null);
String MT = sharedPref.getString("MTOK", null);
if (MID == null || MT == null) {
return false;
} else {
return verifySession(MID, MT);
}
}
@Override
public void processFinish(String s) {
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}
@Override
public void onStart() {
super.onStart();
client.connect();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"helpers Page", // TODO: Define a title for the content shown.
Uri.parse("http://host/path"),
Uri.parse("android-app://com.tfs.appname/http/host/path")
);
AppIndex.AppIndexApi.start(client, viewAction);
}
@Override
public void onStop() {
super.onStop();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"helpers Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app URL is correct.
Uri.parse("android-app://com.tfs.appname/http/host/path")
);
AppIndex.AppIndexApi.end(client, viewAction);
client.disconnect();
}
}
任何帮助将不胜感激!我对这种语言非常非常陌生,所以我仍在掌握它的工作原理。
非常感谢
最佳答案
您的设计存在重大缺陷。错误是显而易见的。在这一行
final helpers helpers = new helpers();
您正在尝试创建 Activity 的对象,这是一种非常非常糟糕的做法。您不能简单地创建这样的 Activity 对象。 Android 中的所有 Activity 都必须经历 Activity 生命周期,以便它们附加有效的上下文。在这种情况下,有效的上下文不会附加到帮助程序实例。所以结果是这一行
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
导致空指针,因为“this”为空。 (为什么?因为这指的是尚未创建的上下文,因为 Activity 没有使用startActivity(intent)启动)
另一件事虽然这不是错误,但您必须使用以大写字母开头的 Activity 名称。这是遵循的约定,将使您的代码更具可读性。由于大小写名称的奇怪使用,您的代码非常困惑。你用小写字母声明你的类,而在某些地方变量是大写的。这会导致困惑。规则是类、接口(interface)等应以大写字母开头,变量应以小写字母开头。
那么在这种情况下你会做什么?
您从未启动 Helper Activity ,我认为您不需要将其显示给用户。也就是说,它需要在没有用户交互的情况下完成一些工作。你应该把它变成一项服务。然后使用 startService(intent) 启动它。
或者您也可以将其创建为 Java 类,具体取决于您的用例。
编辑:顺便说一句,我回答了 another类似的问题有同样的问题,但涉及今天晚些时候的服务。
关于java - Android 应用程序在运行时崩溃 : 'java.lang.String android.content.Context.getPackageName()' ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/37094039/
我有一段代码看起来像这样: void update_clock(uint8_t *time_array) { time_t time = *((time_t *) &time_array[0]
应用程序崩溃了 :( 请帮助我.. 在这方面失败了。我找不到错误?该应用程序可以连接到 iTunesConnect 但它会出错。 谁能根据下面的崩溃报告判断问题出在哪里? share_with_app
小二是新来的实习生,作为技术 leader,我给他安排了一个非常简单的练手任务,把前端 markdown 编辑器里上传的图片保存到服务器端,结果他真的就把图片直接保存到了服务器上,这下可把我气坏了,就
我正在创建一个函数,它将目录路径作为参数传递,或者如果它留空,则提示用户输入。 我已经设置了我的 PATH_MAX=100 和 if 语句来检查 if ((strlen(folder path) +
我已将“arial.ttf”文件(从我的/Windows/Fonts 文件夹中获取)加载到内存中,但是将其传递到 FT_New_Memory_Face 时会崩溃(在 FT_Open_Face 中的某处
我正在尝试在我的计算机上的两个控制台之间进行 rtsp 流。 在控制台 1 上,我有: ffmpeg -rtbufsize 100M -re -f dshow -s 320x240 -i video=
我正在尝试使用 scio_beast在一个项目中。我知道它还没有完成,但这并不重要。我已经设法让它工作得很好。 我现在正在尝试连接到 CloudFlare 后面的服务器,我知道我需要 SNI 才能工作
我有一个带有关联宏的下拉列表,如下所示: Sub Drop() If Range("Hidden1!A1") = "1" Then Sheets("Sheet1").Se
我对 bash 很陌生。我要做的就是运行这个nvvp -vm /usr/lib64/jvm/jre-1.8.0/bin/java无需记住最后的路径。我认为 instafix 就是这样做...... n
我在 Windows 上使用 XAMPP 已经两年左右了,它运行完美,没有崩溃没有问题。 (直到四个月前。) 大约四个月前,我们将服务器/系统升级到了更快的规范。 这是旧规范的内容 - Windows
我面临着一个非常烦人的 android 崩溃,它发生在大约 1% 的 PRODUCTION session 中,应用程序始终在后台运行。 Fatal Exception: android.app.Re
尝试使用下面的函数: public void createObjectType() { try { mCloudDB.createObjectType(ObjectTypeIn
由于我正在进行的一个项目,我在 CF11 管理员中弄乱了类路径,我设法使服务器崩溃,以至于我唯一得到的是一个漂亮的蓝屏和 500 错误.我已经检查了日志,我会把我能做的贴在帖子的底部,但我希望有人会启
关闭。这个问题不满足Stack Overflow guidelines .它目前不接受答案。 想改善这个问题吗?更新问题,使其成为 on-topic对于堆栈溢出。 10 个月前关闭。 Improve
我最近从 xcode 3.x 更新到 4.2,当我在 4.2 中运行应用程序时,我遇到了核心数据问题。我还更新到了 iOS 5,所以问题可能就在那里,我不太确定。 这些应用程序在 3.x 中运行良好,
我是一个相对较新的 iPhone 应用程序开发人员,所以我的知识有点粗略,所以如果这是一个微不足道的问题,请原谅我。 我有一个导航应用程序,它通过在navigationController对象上调用p
if ([MFMailComposeViewController canSendMail]) { MFMailComposeViewController *mailViewController
你能帮我吗? 我正在设置 UILocalNotification,当我尝试设置其 userInfo 字典时,它崩溃了。 fetchedObjects 包含 88 个对象。 这是代码: NSDi
为什么我的代码中突然出现 NSFastEnumeration Mutation Handler 崩溃。我很茫然为什么会突然出现这个崩溃以及如何解决它。 最佳答案 崩溃错误: **** 由于未捕获的异常
当我从表中删除行时,我的应用程序崩溃了。这是我检测到错误和堆栈跟踪的来源。谢谢! //delete row from database - (void)tableView:(UITableView *
我是一名优秀的程序员,十分优秀!