Question

我有这段代码：

09-20 18:06:37.279 21398-21398/info.androidhive.camerafileupload E/AndroidRuntime: FATAL EXCEPTION: main
                                                                               Process: info.androidhive.camerafileupload, PID: 21398
                                                                               java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.camerafileupload/info.androidhive.camerafileupload.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setBackgroundDrawable(android.graphics.drawable.Drawable)' 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.-wrap11(ActivityThread.java)
                                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                   at android.os.Looper.loop(Looper.java:148)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                                   at com.android.internal.os.ZygoteInit$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 'void android.app.ActionBar.setBackgroundDrawable(android.graphics.drawable.Drawable)' on a null object reference
                                                                                   at info.androidhive.camerafileupload.MainActivity.onCreate(MainActivity.java:46)
                                                                                   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.-wrap11(ActivityThread.java) 
                                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                                   at android.os.Looper.loop(Looper.java:148) 
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                                   at java.lang.reflect.Method.invoke(Native Method) 
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

使用Javascript / JQuery时我想隐藏一些部分。但是，上面的代码给了我一个语法错误。

我该怎么做才能比较我的listitem中的id和javascript字符串？我已经尝试使用<script> var array = ["test1", "test2", "test & test"]; $(document).ready(function() { for (i = 0; i < array.length; i++) { $("#" + array[i]).hide(); } }); </script> <ul> <li id="test1"></li> <li id="test2"></li> <li id="test & test"></li> </ul>和"&amp ;"

之类的内容在javascript中切换＆符号

由于我从数据库中获取了listitem的id，因此我不想改变那一方。

Answer 1

您不能在元素的id中使用空格。

您可能不希望在元素的id中使用＆符号，但如果您真的需要，可以使用css选择器中的一个反斜杠转义&，并在jQuery选择器中使用两个反斜杠

在你的例子中：

var array = ["test1", "test2", "test\\&test"];

$(document).ready(function() {
  for (i = 0; i < array.length; i++) {
    $("#" + array[i]).hide();
  }
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<ul>
  <li id="test1"></li>
  <li id="test2"></li>
  <li id="test&test"></li>
</ul>

Answer 2

id不能包含空格

用“test_test”替换你的id“test＆amp; test”，它会起作用。

var array = ["test1", "test2", "test_test"];
$(document).ready(function() {

  for (i = 0; i < array.length; i++) {
    $("#" + array[i]).hide();
  }

});

和js

\\

或者如果你真的需要使用＆符号在js数组中使用var beacons = { "key": { "one": "char", "two": "sue", "three": "johnny" }, "key2": { "one": "char", "two": "sue", "three": "johnny" }, "key3": { "one": "char", "two": "cara", "three": "johnny" } }; var beaconsArray = []; for(var key in beacons) { beaconsArray.push(beacons[key]); } console.log(beaconsArray);

将其转义

Demo

在javascript字符串中使用＆符号

2 个答案: