Question

我想要的只是在editText中设置一些文字。我不想在xml中使用android:text="bla bla bla"因为我得到了用户输入的东西。 Y是这个简单的东西不适合我。我的应用程序成功构建但崩溃了。

aaaa.setText("sss");

我尝试了一个新项目，只是为了验证它的工作原理。好吧，它没有。
我的档案:-(新项目）

package com.rishav.testing;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.EditText;


public class MainActivity extends AppCompatActivity {

    EditText aaaa=(EditText)findViewById(R.id.aaaa);
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        aaaa.setText("sss");
    }
}

布局： -

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.rishav.testing.MainActivity">

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:width="300dp"
        android:id="@+id/aaaa"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

顺便说一句，我正在使用AS 3.0 canary 3 sdk工具26.0.0

错误Logcat： -

06-13 04:02:47.368 14469-14469/com.rishav.t2 I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead.
06-13 04:02:47.371 14469-14469/com.rishav.t2 I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead.
06-13 04:02:47.373 14469-14469/com.rishav.t2 I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead.
06-13 04:02:47.375 14469-14469/com.rishav.t2 I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead.
06-13 04:02:47.377 14469-14469/com.rishav.t2 I/TextInputLayout: EditText added is not a TextInputEditText. Please switch to using that class instead.
06-13 04:02:47.647 14469-14469/com.rishav.t2 W/IInputConnectionWrapper: finishComposingText on inactive InputConnection
06-13 04:02:56.393 14469-14469/com.rishav.t2 I/hifiwi: Signup
06-13 04:02:57.126 14469-14469/com.rishav.t2 I/hifiwi: working atleast
06-13 04:02:57.126 14469-14469/com.rishav.t2 I/hifiwi: working atleast
06-13 04:02:57.128 14469-14469/com.rishav.t2 D/AndroidRuntime: Shutting down VM


                                                               --------- beginning of crash
06-13 04:02:57.129 14469-14469/com.rishav.t2 E/AndroidRuntime: FATAL EXCEPTION: main
                                                               Process: com.rishav.t2, PID: 14469
                                                               java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
                                                                   at com.rishav.t2.SigningActivity.deft(SigningActivity.java:208)
                                                                   at com.rishav.t2.MyDemoListener.onClick(SigningActivity.java:222)
                                                                   at android.support.design.widget.Snackbar$1.onClick(Snackbar.java:255)
                                                                   at android.view.View.performClick(View.java:5637)
                                                                   at android.view.View$PerformClick.run(View.java:22433)
                                                                   at android.os.Handler.handleCallback(Handler.java:751)
                                                                   at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                   at android.os.Looper.loop(Looper.java:154)
                                                                   at android.app.ActivityThread.main(ActivityThread.java:6186)
                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

Answer 1

您可以将视图定义为字段，但不能在其中初始化。

^{技术原因：在类初始化时没有为Activity定义上下文}

public class MainActivity extends AppCompatActivity {

    private EditText aaaa;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        aaaa=(EditText)findViewById(R.id.aaaa);
        aaaa.setText("sss");
    }
}

如果您计划使用其他方法，这也是更好的方法

Answer 2

只需在onCreate中定义EditText，然后在setText中定义

public class MainActivity extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        EditText aaaa=(EditText)findViewById(R.id.aaaa);
        aaaa.setText("sss");
    }
}

Answer 3

您正在尝试在屏幕上创建editText之前访问它。移动这一行

 EditText aaaa=(EditText)findViewById(R.id.aaaa);

之后

setContentView(R.layout.activity_main);
EditText aaaa=(EditText)findViewById(R.id.aaaa);
aaaa.setText("sss");

Answer 4

接下来我要在Kotlin上使用

edit_text_view.text!!.append("some_text")

没有检查，但是我认为在Java中会有类似的东西-

edit_text_view.setText(edit_text_view.getText().append("some_text"));

如果要设置新文本，请首先使用clear()功能（对于Editable -> edit_text_view.getText()）

editText.setText不起作用

4 个答案: