问题描述

Android - 无法从EditText Control读取文本

程序中有一个AlertDialog对话框，使用了一个自定义布局。在OnClick事件中我想读出用户输入的信息。使用了以下的代码：

//Login Dialog            AlertDialog.Builder builder = new AlertDialog.Builder(this);            // Get the layout inflater            LayoutInflater inflater = this.getLayoutInflater();            // Inflate and set the layout for the dialog            // Pass null as the parent view because its going in the dialog layout            builder.setView(inflater.inflate(R.layout.dialog_signin null))            .setPositiveButton(R.string.tvLoginTitle new DialogInterface.OnClickListener() {                   @Override                   public void onClick(DialogInterface dialog int id) {                       String username = ((EditText)findViewById(R.id.loginUsername)).getText().toString();                       String password = ((EditText)findViewById(R.id.loginPassword)).getText().toString();                       System.out.println(username);                       System.out.println(password);                       ConnectionID.loginToServer(cMainActivity username password);                   }               })               .setNegativeButton(R.string.btnExit new DialogInterface.OnClickListener() {                   public void onClick(DialogInterface dialog int id) {                       System.exit(0);                   }               }).show(); 

但是当我想要读出信息的时候，获得一个来自dialog_signin的布局中NullPointerException异常。

<EditText    android:id=""@+id/loginUsername""    android:inputType=""textEmailAddress""    android:layout_width=""match_parent""    android:layout_height=""wrap_content""    android:layout_marginTop=""16dp""    android:layout_marginLeft=""4dp""    android:layout_marginRight=""4dp""    android:layout_marginBottom=""4dp""    android:hint=""@string/tvUsername"" /><EditText    android:id=""@+id/loginPassword""    android:inputType=""textPassword""    android:layout_width=""match_parent""    android:layout_height=""wrap_content""    android:layout_marginTop=""4dp""    android:layout_marginLeft=""4dp""    android:layout_marginRight=""4dp""    android:layout_marginBottom=""16dp""    android:fontFamily=""sans-serif""    android:hint=""@string/tvPassword""/>

解决方案

如果用户名和密码是对话框中的，你应该使用以下代码:

View v = inflater.inflate(R.layout.dialog_signin null); builder.setView(v);String username = ((EditText)v.findViewById(R.id.loginUsername)).getText().toString();String password = ((EditText)v.findViewById(R.id.loginPassword)).getText().toString();

解决方案二：

//Login Dialog        AlertDialog.Builder builder = new AlertDialog.Builder(this);        // Get the layout inflater        LayoutInflater inflater = this.getLayoutInflater();        // Inflate and set the layout for the dialog        // Pass null as the parent view because its going in the dialog layout        View view = inflater.inflate(R.layout.dialog_signin null);        final EditText txtuser = (EditText)findViewById(R.id.loginUsername);        final EditText txtpass = (EditText)findViewById(R.id.loginPassword);        builder.setView(view)        .setPositiveButton(R.string.tvLoginTitle new DialogInterface.OnClickListener() {               @Override               public void onClick(DialogInterface dialog int id) {                   String username = txtuser.getText().toString();                   String password = txtpass.getText().toString();                   System.out.println(username);                   System.out.println(password);                   ConnectionID.loginToServer(cMainActivity username password);               }           })           .setNegativeButton(R.string.btnExit new DialogInterface.OnClickListener() {               public void onClick(DialogInterface dialog int id) {                   // System.exit(0); // don't do this in Android               }           }).show(); 

解决方案三：
我使用以下的对话框后能很好的实现。

Dialog builder = new Dialog(this);builder.setContentView(R.layout.dialog_signin);String username = ((EditText)builder.findViewById(R.id.loginUsername)).getText().toString();String password = ((EditText)builder.findViewById(R.id.loginPassword)).getText().toString();//你的按钮builder.show();