无法从布局中删除视图
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【中文标题】无法从布局中删除视图【英文标题】：Cannot remove a view from layout 【发布时间】：2012-10-30 20:55:13 【问题描述】：我正在创建一个小应用程序，您可以在其中通过单击按钮添加或删除表格行。每当我单击“添加行”按钮时，该按钮都会在布局中添加一个表格行并执行它应该执行的操作。但是，“删除行”不会删除新添加的表格行，但会像预期的那样减少（int count）。我已经工作和搜索了大约 4 到 5 个小时，但我没有运气。代码如下：
int count = 0;
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button buttonAdd = (Button) findViewById(R.id.button1);
Button buttonDel = (Button) findViewById(R.id.button2);
buttonAdd.setOnClickListener(this);
buttonDel.setOnClickListener(this);
public void onClick(View v)
TableLayout tableLayout1;
EditText editText1;
EditText editText2;
TableRow tempRow;
EditText tempText1;
EditText tempText2;
TableRow tableRow1;
tableLayout1 = (TableLayout) findViewById(R.id.tableLayout1);
editText1 = (EditText) findViewById(R.id.editText1);
editText2 = (EditText) findViewById(R.id.editText2);
tempRow = new TableRow(MainActivity.this);
tempText1 = new EditText(MainActivity.this);
tempText2 = new EditText(MainActivity.this);
tempText1.setInputType(InputType.TYPE_CLASS_TEXT);
tempText2.setInputType(InputType.TYPE_NUMBER_FLAG_DECIMAL);
tableRow1 = (TableRow) findViewById(R.id.tableRow1);
tempRow.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
tempText1.setLayoutParams(editText1.getLayoutParams());
tempText2.setLayoutParams(editText2.getLayoutParams());
switch(v.getId())
case R.id.button1:
if(count != 9)
count++;
tempRow.addView(tempText1);
tempRow.addView(tempText2);
tableLayout1.addView(tempRow);
else
final AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create(); //Read Update
alertDialog.setTitle("Error");
alertDialog.setMessage("You can only have 10 rows!");
alertDialog.setButton("Ok", new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
alertDialog.dismiss();
);
alertDialog.show();
break;
case R.id.button2:
if(count != 0)
count--;
tempRow.removeView(tempText1);
tempRow.removeView(tempText2);
tableLayout1.removeView(tempRow);
//tableLayout1.invalidate();
else
final AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create(); //Read Update
alertDialog.setTitle("Error");
alertDialog.setMessage("You must have at least one row!");
alertDialog.setButton("Ok", new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
alertDialog.dismiss();
);
alertDialog.show();
break;
default:
//Do something;
.
10-30 21:22:23.379: E/androidRuntime(3970): FATAL EXCEPTION: main
10-30 21:22:23.379: E/AndroidRuntime(3970): java.lang.NullPointerException
10-30 21:22:23.379: E/AndroidRuntime(3970): at com.android.hopegpacalc.MainActivity.onClick(MainActivity.java:57)
10-30 21:22:23.379: E/AndroidRuntime(3970): at android.view.View.performClick(View.java:3511)
10-30 21:22:23.379: E/AndroidRuntime(3970): at android.view.View$PerformClick.run(View.java:14105)
10-30 21:22:23.379: E/AndroidRuntime(3970): at android.os.Handler.handleCallback(Handler.java:605)
10-30 21:22:23.379: E/AndroidRuntime(3970): at android.os.Handler.dispatchMessage(Handler.java:92)
10-30 21:22:23.379: E/AndroidRuntime(3970): at android.os.Looper.loop(Looper.java:137)
10-30 21:22:23.379: E/AndroidRuntime(3970): at android.app.ActivityThread.main(ActivityThread.java:4424)
10-30 21:22:23.379: E/AndroidRuntime(3970): at java.lang.reflect.Method.invokeNative(Native Method)
10-30 21:22:23.379: E/AndroidRuntime(3970): at java.lang.reflect.Method.invoke(Method.java:511)
10-30 21:22:23.379: E/AndroidRuntime(3970): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-30 21:22:23.379: E/AndroidRuntime(3970): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-30 21:22:23.379: E/AndroidRuntime(3970): at dalvik.system.NativeStart.main(Native Method)
【问题讨论】：
【参考方案1】：这是组织问题，试试这个：
public void onClick(View v)
// These should be class variables, like count, you don't need to re-find it on every click
TableLayout tableLayout1 = (TableLayout) findViewById(R.id.tableLayout1);
EditText editText1 = (EditText) findViewById(R.id.editText1);
EditText editText2 = (EditText) findViewById(R.id.editText2);
switch(v.getId())
case R.id.button1:
if(count != 9)
count++;
// Create the row only when the add button is clicked
TableRow tempRow = new TableRow(MainActivity.this);
EditText tempText1 = new EditText(MainActivity.this);
EditText tempText2 = new EditText(MainActivity.this);
tempText1.setInputType(InputType.TYPE_CLASS_TEXT);
tempText2.setInputType(InputType.TYPE_NUMBER_FLAG_DECIMAL);
tempRow.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
tempText1.setLayoutParams(editText1.getLayoutParams());
tempText2.setLayoutParams(editText2.getLayoutParams());
tempRow.addView(tempText1);
tempRow.addView(tempText2);
tableLayout1.addView(tempRow);
else
// Consider using Activity's showDialog() method, to reuse this "error" dialog rather than create a new one every time
final AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create(); //Read Update
alertDialog.setTitle("Error");
alertDialog.setMessage("You can only have 10 rows!");
alertDialog.setButton("Ok", new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
alertDialog.dismiss();
);
alertDialog.show();
break;
case R.id.button2:
if(count != 0)
// Remove the last row at count or use "tableLayout1.getChildCount() - 1"
tableLayout1.removeView(tableLayout1.getChildAt(count));
count--;
else
// Consider reusing the other "error" Dialog and simply changing the message
final AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this).create(); //Read Update
alertDialog.setTitle("Error");
alertDialog.setMessage("You must have at least one row!");
alertDialog.setButton("Ok", new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
alertDialog.dismiss();
);
alertDialog.show();
break;
default:
//Do something;
【讨论】：
您先生是个天才。谢谢！我现在唯一的问题是，在添加一行后，删除该行，然后尝试再次添加一个，我在第 57 行收到 NullPointerException。它将异常指向“tempText1.setLayoutParams(editText1.getLayoutParams());” 这很奇怪，可以将所有 LogCat 错误编辑到您的问题中吗？所以我可以看到发生了什么。【参考方案2】：每次执行 onClick 时，您的代码都会创建一个新的 TableRow。只有在要添加行时才应该这样做。当您想删除一个时，您必须使用findViewById( id ) 在现有视图中找到要删除的行，然后在该对象上运行removeView。
case R.id.button2:
if ( count != 0 )
count--;
tempRow = (TableRow)findViewById( idoftablerowtodelete );
tableLayout1.removeView( tempRow );
这确实意味着您必须在创建表格时使用setId 在每个表格行上设置一个 ID，并对其进行跟踪。
【讨论】：
【参考方案3】：您的删除代码是“删除”实际上不在表中的临时视图（例如tempText1） - 它们是在onClick 方法中动态创建的。不要在进入onClick 后立即实例化所有这些对象，而是在每个 switch 语句案例的主体中这样做。对于添加按钮，只需复制和粘贴即可。对于删除，将对象设置为等于要删除的行。
您似乎没有办法选择要删除的行，但假设您在其他地方执行此操作，您可以使用TableLayout.removeViewAt(int index) 来选择哪一行。如果你有视图本身而不是索引，还有TableLayout.removeView(View view)。
【讨论】：
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