Question

我希望这是一个非常基本的东西，我只是没有看到 - 但我想知道为什么以下语句调用更新客户端的方法，在update方法的返回行引起NullPointerException。

如果有帮助知道，我有插入并选择工作正常并通过调试我知道update语句在执行之前存储了所有三个变量但从未执行。

方法调用

public void onSaveButtonClick(View v) {

    DBAdapter db = new DBAdapter(this);

    // Create and set fields
    EditText nameField = (EditText) findViewById(R.id.EditText_Name);
    EditText emailField = (EditText) findViewById(R.id.EditText_Email);

    name = nameField.toString();
    email = emailField.toString();

    db.updateClient(_id, "Test Name", "Test Email");
    Toast.makeText(PTViewClient.this,"TODO: Save Button Functionality", Toast.LENGTH_SHORT).show();
}

更新客户端方法抛出NullPointerException

        public boolean updateClient(long clientID, String name, String email) 
    {
        ContentValues args = new ContentValues();
        args.put(KEY_CLIENT_NAME, name);
        args.put(KEY_CLIENT_EMAIL, email);
        return db.update(DATABASE_CLIENTS, args, KEY_CLIENT_ID + "=" + clientID, null) > 0;
    }

堆栈跟踪

05-15 12:47:02.978: E/AndroidRuntime(22110): FATAL EXCEPTION: main

05-15 12:47:02.978: E/AndroidRuntime(22110): java.lang.IllegalStateException: Could not execute method of the activity
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.view.View$1.onClick(View.java:3599)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.view.View.performClick(View.java:4204)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.view.View$PerformClick.run(View.java:17355)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.os.Handler.handleCallback(Handler.java:725)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.os.Handler.dispatchMessage(Handler.java:92)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.os.Looper.loop(Looper.java:137)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.app.ActivityThread.main(ActivityThread.java:5041)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at java.lang.reflect.Method.invokeNative(Native Method)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at java.lang.reflect.Method.invoke(Method.java:511)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at dalvik.system.NativeStart.main(Native Method)
05-15 12:47:02.978: E/AndroidRuntime(22110): Caused by: java.lang.reflect.InvocationTargetException
05-15 12:47:02.978: E/AndroidRuntime(22110):    at java.lang.reflect.Method.invokeNative(Native Method)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at java.lang.reflect.Method.invoke(Method.java:511)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at android.view.View$1.onClick(View.java:3594)
05-15 12:47:02.978: E/AndroidRuntime(22110):    ... 11 more
05-15 12:47:02.978: E/AndroidRuntime(22110): Caused by: java.lang.NullPointerException
05-15 12:47:02.978: E/AndroidRuntime(22110):    at com.personaltrainer.DBAdapter.updateClient(DBAdapter.java:173)
05-15 12:47:02.978: E/AndroidRuntime(22110):    at com.personaltrainer.PTViewClient.onSaveButtonClick(PTViewClient.java:124)
05-15 12:47:02.978: E/AndroidRuntime(22110):    ... 14 more

Answer 1

在调用

之前，只需检查db和_id是否为空指针

db.updateClient(_id, "Test Name", "Test Email");

Answer 2

使用这种方式

return db.update(DATABASE_CLIENTS,  KEY_CLIENT_ID + "=" + clientID, null) > 0;

Answer 3

您需要打开数据库

DBAdapter db = new DBAdapter(this);
db.open();

SQLite更新行上的NullPointerException

3 个答案: