80

我想在editText中有常量文本，例如：

http://<here_user_can_write>

用户应该无法从“ http://”中删除任何字符，我对此进行了搜索并发现了这个：

editText.setFilters(new InputFilter[] {
    new InputFilter() {
        public CharSequence filter(CharSequence src, int start,
            int end, Spanned dst, int dstart, int dend) {
            return src.length() < 1 ? dst.subSequence(dstart, dend) : "";
        }
    }
});

但我不知道它是否限制用户从头到尾不删除任何字符限制。我也无法理解 Spanned 类的使用。

如果我们可以放入TextView内部，一种方法将是一个不错的选择，EditText但我认为这在 Android 中是不可能的，因为两者都是视图，这可能吗？

4

16 回答 16

165

你试过这个方法吗？

final EditText edt = (EditText) findViewById(R.id.editText1);

edt.setText("http://");
Selection.setSelection(edt.getText(), edt.getText().length());


edt.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            // TODO Auto-generated method stub

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable s) {
            if(!s.toString().startsWith("http://")){
                edt.setText("http://");
                Selection.setSelection(edt.getText(), edt.getText().length());

            }

        }
    });
于 2013-01-07T12:04:53.007 回答
44

从材料设计库1.2.0-alpha01版本开始，文本字段支持前缀和后缀：

<com.google.android.material.textfield.TextInputLayout
        app:prefixText="Price: "
        app:prefixTextAppearance="..."
        app:prefixTextColor="..."
        app:suffixText="Dollar"
        app:suffixTextColor="..."
        app:suffixTextAppearance="...">

    <com.google.android.material.textfield.TextInputEditText .../>

</com.google.android.material.textfield.TextInputLayout>

我认为唯一的缺点是后缀固定在文本字段的末尾，并且没有选项可以使其与输入文本一起流动。您可以为此问题投票。

于 2019-11-09T13:13:03.337 回答
16

这就是你可以用一个实际做到的方式InputFilter：

final String prefix = "http://"
editText.setText(prefix);

editText.setFilters(new InputFilter[] {
    new InputFilter() {
      @Override
      public CharSequence filter(final CharSequence source, final int start,
          final int end, final Spanned dest, final int dstart, final int dend) {
        final int newStart = Math.max(prefix.length(), dstart);
        final int newEnd = Math.max(prefix.length(), dend);
        if (newStart != dstart || newEnd != dend) {
          final SpannableStringBuilder builder = new SpannableStringBuilder(dest);
          builder.replace(newStart, newEnd, source);
          if (source instanceof Spanned) {
            TextUtils.copySpansFrom(
                (Spanned) source, 0, source.length(), null, builder, newStart);
          }
          Selection.setSelection(builder, newStart + source.length());
          return builder;
        } else {
          return null;
        }
      }
    }
});

如果您还希望前缀不可选，您可以添加以下代码。

final SpanWatcher watcher = new SpanWatcher() {
  @Override
  public void onSpanAdded(final Spannable text, final Object what,
      final int start, final int end) {
    // Nothing here.
  }

  @Override
  public void onSpanRemoved(final Spannable text, final Object what, 
      final int start, final int end) {
    // Nothing here.
  }

  @Override
  public void onSpanChanged(final Spannable text, final Object what, 
      final int ostart, final int oend, final int nstart, final int nend) {
    if (what == Selection.SELECTION_START) {
      if (nstart < prefix.length()) {
        final int end = Math.max(prefix.length(), Selection.getSelectionEnd(text));
        Selection.setSelection(text, prefix.length(), end);
      }
    } else if (what == Selection.SELECTION_END) {
      final int start = Math.max(prefix.length(), Selection.getSelectionEnd(text));
      final int end = Math.max(start, nstart);
      if (end != nstart) {
        Selection.setSelection(text, start, end);
      }
    }
  }
};

editText.getText().setSpan(watcher, 0, 0, Spanned.SPAN_INCLUSIVE_EXCLUSIVE);
于 2016-04-03T17:58:49.397 回答
10

@Rajitha Siriwardena 的回答有一点问题。它假设除了后缀之外的整个字符串在后缀之前已经被删除，如果你有字符串

http://stackoverflow.com/

并尝试删除http://您将删除的任何部分stackoverflow.com/仅导致http://.

我还添加了一个检查，以防用户尝试在前缀之前输入。

 @Override
 public void afterTextChanged(Editable s) {
     String prefix = "http://";
     if (!s.toString().startsWith(prefix)) {
         String cleanString;
         String deletedPrefix = prefix.substring(0, prefix.length() - 1);
         if (s.toString().startsWith(deletedPrefix)) {
             cleanString = s.toString().replaceAll(deletedPrefix, "");
         } else {
             cleanString = s.toString().replaceAll(prefix, "");
         }
         editText.setText(prefix + cleanString);
         editText.setSelection(prefix.length());
    }
}

注意：这不处理用户尝试仅在前后编辑前缀本身的情况。

于 2015-01-22T23:17:08.847 回答
7

取自 Ali Muzaffar 的博客，有关详细信息，请参阅原始帖子。

使用自定义EditTextView 绘制前缀文本并根据前缀文本大小添加填充：

public class PrefixEditText extends EditText {

private String mPrefix = "$"; // add your prefix here for example $
private Rect mPrefixRect = new Rect(); // actual prefix size

public PrefixEditText(Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    getPaint().getTextBounds(mPrefix, 0, mPrefix.length(), mPrefixRect);
    mPrefixRect.right += getPaint().measureText(" "); // add some offset

    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawText(mPrefix, super.getCompoundPaddingLeft(), getBaseline(), getPaint());
}

@Override
public int getCompoundPaddingLeft() {
    return super.getCompoundPaddingLeft() + mPrefixRect.width();
}
}
于 2017-01-30T04:52:53.627 回答
6

你几乎是对的，试试

private final String PREFIX="http://";

editText.setFilters(new InputFilter[]{new InputFilter() {
            @Override
            public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int
                    dend) {
                return dstart<PREFIX.length()?dest.subSequence(dstart,dend):null;
            }
        }});
于 2015-10-14T11:17:26.297 回答
5

将自定义前缀添加到您的编辑文本的代码（前缀不可编辑）

Ali Muzaffar 来自 Medium 的代码

public class PrefixEditText extends AppCompatEditText {
    float originalLeftPadding = -1;

    public PrefixEditText(Context context) {
        super(context);
    }

    public PrefixEditText(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public PrefixEditText(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        calculatePrefix();
    }

    private void calculatePrefix() {
        if (originalLeftPadding == -1) {
            String prefix = (String) getTag();
            float[] widths = new float[prefix.length()];
            getPaint().getTextWidths(prefix, widths);
            float textWidth = 0;
            for (float w : widths) {
                textWidth += w;
            }
            originalLeftPadding = getCompoundPaddingLeft();
            setPadding((int) (textWidth + originalLeftPadding),
                getPaddingRight(), getPaddingTop(),
                getPaddingBottom());
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        String prefix = (String) getTag();
        canvas.drawText(prefix, originalLeftPadding, getLineBounds(0, null), getPaint());
    }
}

和 XML

<com.yourClassPath.PrefixEditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="bottom"
    android:textSize="14sp"
    android:tag="€ " />
于 2017-08-31T10:05:14.203 回答
4

用于此目的的易于使用的 Kotlin 扩展功能

fun EditText.stickPrefix(prefix: String) {
    this.addTextChangedListener(afterTextChanged = {
        if (!it.toString().startsWith(prefix) && it?.isNotEmpty() == true) {
            this.setText(prefix + this.text)
            this.setSelection(this.length())

        }
    })
}
//someEditText.stickPrefix("+")
于 2020-10-26T18:21:40.330 回答
3

我知道我正在恢复一篇旧帖子，但我想与社区分享我这些天一直在努力解决这个话题的社区，我发现放置一个TextView不仅EditText是完全可行的（回答问题的第二部分） ，在这种情况下，当在起始位置需要常量文本时更多，但也更可取。此外，光标甚至根本不会在“可变”文本之前移动，这是一种优雅的效果。我更喜欢这个解决方案，因为它不会增加我的应用程序的工作量和复杂性以及监听器等等。

这是我的解决方案的示例代码：

<RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_marginStart="3dp"
        android:text="http://" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textUri"
        android:paddingStart="choose an appropriate padding" />
</RelativeLayout>

通过将视图包含在 a 中，RelativeLayout它们将重叠。这里的技巧是使用 , 的属性android:paddingStart使EditText文本在TextView,之后开始至少在使用材质主题时会发生这种情况）。android:layout_centerVertical="true"android:layout_marginStart="3dp"TextViewEditText

于 2016-10-05T16:57:18.200 回答
3

我制作了 Kotlin 扩展函数来添加前缀EditText

fun EditText.addPrefix(prefix: String) {
        var text = ""
        var isPrefixModified = false
        val formattedPrefix = "$prefix "
        var lastCharSequence: CharSequence? = null

        val setEditText: () -> Unit = {
            setText(text)
            Selection.setSelection(editableText, text.length)
        }

        this.addTextChangedListener(object : TextWatcher {
            override fun afterTextChanged(editable: Editable?) {
                val newText = editable.toString()

                when {
                    isPrefixModified -> {
                        isPrefixModified = false
                        setEditText()
                    }
                    isTryingToDeletePrefix(newText) -> {
                        setEditText()
                    }
                    isNewInput(newText) -> {
                        text = "$formattedPrefix$newText"
                        setEditText()
                    }
                    else -> {
                        text = newText
                    }
                }
            }

            override fun beforeTextChanged(charSequence: CharSequence?, start: Int,
                                           count: Int, after: Int) {
                charSequence?.let {
                    if (it != lastCharSequence && it.isNotEmpty() && start <= prefix.length) {
                        isPrefixModified = true
                    }
                    lastCharSequence = charSequence
                }
            }

            override fun onTextChanged(charSequence: CharSequence?, start: Int,
                                       before: Int, count: Int) {
                // Ignore
            }

            private fun isTryingToDeletePrefix(newText: String) =
                    text.isNotEmpty() && newText.length < text.length && isNewInput(newText)

            private fun isNewInput(newText: String) = !newText.contains(formattedPrefix)
        })
    }
于 2020-07-07T07:16:53.883 回答
2

这基本上是在电话号码的编辑文本字段中添加前缀“+91”。

1.将此代码添加到活动的oncreate（）中

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

   // Write other things......//

   etPhoneNumber.setFilters(new InputFilter[]{getPhoneFilter(),newInputFilter.LengthFilter(13)});

    etPhoneNumber.setOnFocusChangeListener(new View.OnFocusChangeListener() {
        @Override
        public void onFocusChange(View v, boolean hasFocus) {
            if (hasFocus) {
                if (etPhoneNumber.getText().toString().isEmpty()) {
                    etPhoneNumber.setText("+91");
                    Selection.setSelection(etPhoneNumber.getText(), etPhoneNumber.getText().length());                    }
            } else {
                if (etPhoneNumber.getText().toString().equalsIgnoreCase("+91")) {
                    etPhoneNumber.setFilters(new InputFilter[]{});
                    etPhoneNumber.setText("");
                    etPhoneNumber.setFilters(new InputFilter[]{getPhoneFilter(),new InputFilter.LengthFilter(13)});

                }
            }
        }
    });
}

2.声明一个名为getPhoneFilter()的方法

    private InputFilter getPhoneFilter() {

    Selection.setSelection(etPhoneNumber.getText(), etPhoneNumber.getText().length());

    etPhoneNumber.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                                      int after) {
        }

        @Override
        public void afterTextChanged(Editable s) {
            if(!s.toString().startsWith("+91")){
                if (etPhoneNumber.getFilters() != null && etPhoneNumber.getFilters().length > 0) {
                    etPhoneNumber.setText("+91");
                    Selection.setSelection(etPhoneNumber.getText(), etPhoneNumber.getText().length());
                }
            }
        }
    });

     // Input filter to restrict user to enter only digits..
    InputFilter filter = new InputFilter() {

        public CharSequence filter(CharSequence source, int start, int end,
                                   Spanned dest, int dstart, int dend) {

            for (int i = start; i < end; i++) {

                if (!String.valueOf(getString(R.string.digits_number)).contains(String.valueOf(source.charAt(i)))) {
                    return "";
                }
            }
            return null;
        }
    };
    return filter;
}

3.在你的值文件中声明“digits_number”

    <string name="digits_number">1234567890+</string>
于 2018-07-18T14:21:25.210 回答
2

基于@demaksee评论。我扩展了 EditText 并覆盖了 onSelectionChanged 函数。所以用户甚至不能编辑前缀。非常简单实用。科特林：

private var prefix : String? = ""

override fun onSelectionChanged(selStart: Int, selEnd: Int) {
    if (prefix != null && prefix!!.isNotBlank()) {
        var finalStart = selStart
        var finalEnd = selEnd

        val prefixLength = prefix!!.length
        if (prefixLength > selStart) {
            finalStart = prefixLength
        }

        if (prefixLength > selEnd) {
            finalEnd = prefixLength
        }

        if (finalStart == selStart && finalEnd == selEnd) {
            super.onSelectionChanged(finalStart, finalEnd)
        } else {
            val startWithPrefix = text?.startsWith(prefix ?: "") ?: prefix.isNullOrBlank()
            if (!startWithPrefix) {
                setText(prefix)
            }

            setSelection(finalStart, finalEnd)
        }
    }
}

public fun setPrefix(prefix: String) {
    editText.setText(prefix)
    editText.setSelection(prefix.length)
    this.prefix = prefix
}
于 2019-09-04T11:43:30.673 回答
1

这是一个效率较低的解决方案，它应该处理在前缀周围删除/插入字符或单词的所有情况。

prefix = "http://"
extra = "ahhttp://"
differencePrefix(prefix, extra) = "aht"

代码：

public static String differencePrefix(String prefix, String extra) {
    if (extra.length() < prefix.length()) return "";
    StringBuilder sb = new StringBuilder();
    StringBuilder eb = new StringBuilder();
    int p = 0;
    for (int i = 0; i < extra.length(); i++) {
        if (i >= prefix.length()) {
            while(p < extra.length()) {
                eb.append(extra.charAt(p));
                p++;
            }
            break;
        }
        if (p >= extra.length()) break;
        char pchar = extra.charAt(p);
        char ichar = prefix.charAt(i);
        while(pchar != ichar) {
            //check if char was deleted
            int c = i + 1;
            if (c < prefix.length()) {
                char cchar = prefix.charAt(c);
                if (cchar == pchar) {
                    break;
                }
            }
            sb.append(pchar);
            p++;
            if (p >= extra.length()) break;
            pchar = extra.charAt(p);
        }
        p++;
    }

    return eb.toString() + sb.toString();
}

你可以像这样使用它

editText.addTextChangedListener(new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {

    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {

    }

    @Override
    public void afterTextChanged(Editable s) {
        String input = s.toString();
        if (!input.startsWith(prefix)) {
            String extra = differencePrefix(prefix, input);
            String newInput = prefix + extra;
            editText.setText(newInput);
            editText.setSelection(newInput.length());
        }
    }
});
于 2015-09-14T22:38:09.870 回答
1

我刚刚找到了如何使前缀不可编辑以及如果您尝试删除前缀如何保存文本的解决方案。这非常接近@Rajitha Siriwardena 的答案。您错过的只是在应用任何更改之前保存文本。它将在 afterTextChanged(...) 中恢复。

代码：

final String prefix = "http://";
editText.setText(prefix);
Selection.setSelection(editText.getText(), editText.getText().length());

editText.addTextChangedListener(new TextWatcher() {
    String text;
    @Override
    public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
        text = charSequence.toString();
    }

    @Override
    public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
    }

    @Override
    public void afterTextChanged(Editable editable) {
        if (!editable.toString().startsWith(prefix)) {
            editText.setText(text);
            Selection.setSelection(editText.getText(), editText.getText().length());
        }
    }
});
于 2018-03-04T20:31:14.620 回答
1 
    EditText msg=new EditText(getContext());
                msg.setSingleLine(true);
                msg.setSingleLine();
                msg.setId(View.generateViewId());
                msg.measure(0,0);



                TextView count=new TextView(getContext());
                count.setTextColor(Color.parseColor("#666666"));
                count.setText("20");
                count.setPadding(0,0,(int)Abstract.getDIP(getContext(),10),0);
                count.measure(0,0);
float tenPIX =TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,10,getContext().getResources().getDisplayMetrics());

 msg.setPadding((int)tenPIX,(int)tenPIX,(int)(int)tenPIX+count.getMeasuredWidth(),(int)tenPIX);


                RelativeLayout ll1=new RelativeLayout(getContext());
                ll1.addView(msg,new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));

LayoutParams countlp=new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
                countlp.addRule(RelativeLayout.ALIGN_END,msg.getId());
                countlp.addRule(RelativeLayout.ALIGN_BASELINE,msg.getId());
                ll1.addView(count,countlp);
于 2018-04-07T07:21:54.300 回答
1

下面的代码对我有用。它处理用户编辑前缀、删除它、从缓冲区插入文本、更改选定文本的情况。如果用户更改前缀，则焦点移动到前缀的末尾。

    final String prefix = "http://";
    final String[] aLastText = {prefix};
    et.setText(prefix);
    et.addTextChangedListener(new TextWatcher() {
        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {}
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
        @Override
        public void afterTextChanged(Editable sNew) {

            if (!sNew.toString().startsWith(prefix)) {
                String sLast = aLastText[0];
                boolean isRemoving = sNew.length() < sLast.length();

                int start;
                int end = sNew.length() - 1;
                for (start = 0; start < sLast.length() && start < sNew.length(); start++) {
                    if (sLast.charAt(start) != sNew.charAt(start)) 
                        break;
                }
                int k = sLast.length() - 1;
                for (; end >= start && k >= 0; end--, k--) {
                    if (sLast.charAt(k) != sNew.charAt(end)) 
                        break;
                }
                String sEdited = sNew.toString().substring(start, ++end);
                k += isRemoving ? 1 : 0;
                k = k < prefix.length() ? prefix.length() : k;
                String sSuffix = sLast.substring(k, sLast.length());

                et.setText(prefix + sEdited + sSuffix);
                et.setSelection(et.getText().length() - sSuffix.length());
            }
            aLastText[0] = et.getText().toString();
        }
    });

例子：

ht5tp://localhost, 5http://localhost, http://5/localhost -> http://5localhost

http:localhost -> http://localhost

于 2019-01-17T14:10:49.090 回答