android 还可以输入多少个字符

关键代码：

//监听输入字数
etContent.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) {
mTitle = etContent.getText().toString();
leftTextNum = getLeftTextNum();
tvLeft.setText("还可以输入:" + leftTextNum + "个字");
}

@Override
public void afterTextChanged(Editable s) {
}
});

实例：

private void initData() {
//判断还可以输入多少个字数
etComment.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) {

String mWriteText = etComment.getText().toString();
String mLeftText = String.valueOf(256 - mWriteText.length());
tvPerWrite.setText("还可以输入: "+mLeftText+"个字符");

}

@Override
public void afterTextChanged(Editable s) {

}
});

}

<RelativeLayout
android:id="@+id/rl_comment_content"
android:layout_width="260dp"
android:layout_height="140dp"
android:layout_below="@+id/tv_comment"
android:layout_centerHorizontal="true"
android:layout_marginTop="20dp"
android:background="@drawable/comment_edittext">

<EditText
android:id="@+id/et_comment"
android:layout_width="match_parent"
android:layout_height="120dp"
android:background="@null"
android:gravity="top"
android:hint="填写您的评价和建议"
android:textColorHint="@color/color_cbccd1"
android:textSize="15sp"
android:maxLength="256"
/>

<TextView
android:id="@+id/tv_per_write"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:text="还可以输入"
android:textColor="@color/color_cbccd1"
android:textSize="14sp" />

</RelativeLayout>