android - getText() 和 setText() 在 android 代码中不起作用

Question

你好我正在创建一个 android 应用程序，它填写一个表单并将详细信息以字符串的形式发送到服务器端的 php 脚本。但问题是我无法提取或提供 EditText 字段的任何新值。请帮忙..我的代码有点像这样..

EditText id_st1_event_edit,id_st1_date_edit,id_st1_time_edit,id_st1_venue_edit;
EditText id_st2_name_edit,id_st2_phone_edit,id_st2_phone_edit2,id_st2_email_edit,id_st2_email_edit2;
EditText id_st3_desc_edit;

//Declaration of static IP Address of the server side 
public static String addr = "10.0.2.2";
public String sendsentence;

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

    //Attaching the entities with their proper ID Components
    welcome=(TextView)findViewById(R.id.welcome_message);
    create_event=(TextView)findViewById(R.id.id_create_event);
    browse_event=(TextView)findViewById(R.id.id_browse_event);
    about_us=(TextView)findViewById(R.id.id_about_us);

    id_st1_time=(TextView)findViewById(R.id.id_st1_time);
    id_st1_venue=(TextView)findViewById(R.id.id_st1_venue);
    id_st1_event=(TextView)findViewById(R.id.id_st1_event);
    id_st1_date=(TextView)findViewById(R.id.id_st1_date);
    id_st1_next=(TextView)findViewById(R.id.id_st1_next);

    id_st2_name=(TextView)findViewById(R.id.id_st2_name);
    id_st2_phone=(TextView)findViewById(R.id.id_st2_phone);
    id_st2_email=(TextView)findViewById(R.id.id_st2_email);
    about_organiser=(TextView)findViewById(R.id.about_organiser);

    id_st3_event_description=(TextView)findViewById(R.id.id_st3_event_description);

    id_st1_time_edit=(EditText)findViewById(R.id.id_st1_time_edit);
    id_st1_date_edit=(EditText)findViewById(R.id.id_st1_date_edit);
    id_st1_event_edit=(EditText)findViewById(R.id.id_st1_event_edit);
    id_st1_venue_edit=(EditText)findViewById(R.id.id_st1_venue_edit);

    id_st2_name_edit=(EditText)findViewById(R.id.id_st2_name_edit);
    id_st2_phone_edit=(EditText)findViewById(R.id.id_st2_phone_edit);
    id_st2_phone_edit2=(EditText)findViewById(R.id.id_st2_phone_edit2);
    id_st2_email_edit=(EditText)findViewById(R.id.id_st2_email_edit);
    id_st2_email_edit2=(EditText)findViewById(R.id.id_st2_email_edit2);

    id_st3_desc_edit=(EditText)findViewById(R.id.id_st3_desc_edit);

    butt_submit=(Button)findViewById(R.id.butt_submit);

}

public void onBackPressed() {
    Toast.makeText(getApplicationContext()," Exiting Application ", Toast.LENGTH_SHORT).show();
    finish();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

public void createNew(View V)
{

    setContentView(R.layout.create_new_event);
    tabhost= (TabHost)findViewById(R.id.tabhost);
    tabhost.setup();        
     TabHost.TabSpec spec;
        spec=tabhost.newTabSpec("tag1");
        spec.setContent(R.id.tab1);
        spec.setIndicator("Step 1");
        tabhost.addTab(spec);

        spec=tabhost.newTabSpec("tag2");
        spec.setContent(R.id.tab2);
        spec.setIndicator("Step 2");
        tabhost.addTab(spec);

        spec=tabhost.newTabSpec("tag3");
        spec.setContent(R.id.tab3);
        spec.setIndicator("Step 3");
        tabhost.addTab(spec);
}

public void aboutUs(View V)
{
    setContentView(R.layout.about_us);
}

public void browseEvent(View V)
{
    setContentView(R.layout.browse_new);
}

public void to_next(View v)
{
    tabhost= (TabHost)findViewById(R.id.tabhost);
    tabhost.setCurrentTab((tabhost.getCurrentTab())+1);

}

public void to_previous(View v)
{
    tabhost= (TabHost)findViewById(R.id.tabhost);
    tabhost.setCurrentTab((tabhost.getCurrentTab())-1);     
}

public void submit_data(View V)
{
    try{
        new DoSocketProgramming(this).execute("10.0.2.2");
    }
    catch(Exception e){
        Toast.makeText(getApplicationContext(), "problem here", Toast.LENGTH_SHORT).show();
    }
    Toast.makeText(getApplicationContext(), "created till here", Toast.LENGTH_SHORT).show();
}

public class DoSocketProgramming extends AsyncTask<String, Void, String>
{
    String sendsentence="create table ";
    String recvsentence;
    Context context;

    //sendsentence=id_st1_event_edit.getText().toString();
    private DoSocketProgramming(Context context){
        this.context = context; 
    }

    protected void onPreExecute()
    {   
        Toast.makeText(getApplicationContext(), "this is preExecute", Toast.LENGTH_LONG).show();
    }
    protected String doInBackground(String... params) {
        // TODO Auto-generated method stub
        try{            
            Socket con=new Socket(addr,1678);
            DataInputStream dis= new DataInputStream(con.getInputStream());
            DataOutputStream dos=new DataOutputStream(con.getOutputStream());

            dos.writeUTF(sendsentence);
            recvsentence=dis.readUTF();

        }catch(Exception e)
            {
            e.printStackTrace();
            }
        Log.d("myApp","i've reached at doinbackground");
        return recvsentence;
    }

    protected void onPostExecute(String result) {
        try{
            Log.d("myApp","i've reached on PostExecute");
            Toast.makeText(context, "this is post execute "+ result, Toast.LENGTH_LONG).show();
        }
        catch(Exception e)
            {
                e.printStackTrace();
            }
    }

}}

DoSocketProgramming 类中的“sendsentence”在上面的 php 端正确显示，但是当我尝试使用 GetText() 或 SetText() 函数向其添加一些文本时，我的应用程序崩溃了。我该怎么办？？

Answer 1

这个问题真的没什么可继续的，但我会试一试。

使用 getText() 显示的唯一一行是这一行...

//sendsentence=id_st1_event_edit.getText().toString();

正如问题评论中提到的，最可能的原因是 NullPointerException。如果是这种情况，则 id_st1_event_edit 为空。

如果是这种情况，则 onCreate(...) 中的以下行

id_st1_date_edit=(EditText)findViewById(R.id.id_st1_date_edit);

...无法找到资源 ID 为 R.id.id_st1_date_edit 的 EditText，这表明特定的 EditText 不在你的 activity_main.xml 布局文件。

记住你在几个地方调用 setContentView(...) 我猜它实际上是在 browse_new.xml 布局文件(或另一个布局文件)。

如果是这种情况，那么您的问题是您只能使用 findViewById(...) 在当前内容 View 中查找 View 。将对 findViewById(...) 的调用移动到更改内容 View 的方法。示例...

public void browseEvent(View V)
{
    setContentView(R.layout.browse_new);
    // Call findViewById(...) for any widgets in browse_new.xml here
}