微信朋友圈中，如果好友發表的文字過長，會自動收縮起來，底下有提示，當點選“顯示更多”時才會展開。

首先定義佈局檔案（很簡單，不解釋）：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/desc_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4.0dip"
        android:gravity="center_vertical"
        android:textColor="#ff000000"
        android:textSize="14.0dip" />

    <TextView
        android:id="@+id/desc_op_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4.0dip"
        android:gravity="center"
        android:singleLine="true"
        android:textColor="#ff576b95"
        android:textSize="14.0dip"
        android:visibility="gone" />

</LinearLayout>
 

文字：

    <string name="desc_shrinkup">收起</string>
    <string name="desc_spread">顯示更多</string>

接下來就是對文字的處理，原理就是設定TextView最大行數。

先判斷文字是否超過了規定的行數，如果沒超過，不顯現“顯示更多”的文字提示。當文字超過了，就顯示“顯示更多”的文字提示。使用者點選“顯示更多”後，設定最大行數為最大。

補一句：微信的預設最大行數是10行，我這裡設定是2行。你可以自行設定該值DEFAULT_MAX_LINE_COUNT。

程式碼如下：

public class CollapsibleTextView extends LinearLayout implements
        OnClickListener {

    /** default text show max lines */
    private static final int DEFAULT_MAX_LINE_COUNT = 2;

    private static final int COLLAPSIBLE_STATE_NONE = 0;
    private static final int COLLAPSIBLE_STATE_SHRINKUP = 1;
    private static final int COLLAPSIBLE_STATE_SPREAD = 2;

    private TextView desc;
    private TextView descOp;

    private String shrinkup;
    private String spread;
    private int mState;
    private boolean flag;

    public CollapsibleTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        shrinkup = context.getString(R.string.desc_shrinkup);
        spread = context.getString(R.string.desc_spread);
        View view = inflate(context, R.layout.collapsible_textview, this);
        view.setPadding(0, -1, 0, 0);
        desc = (TextView) view.findViewById(R.id.desc_tv);
        descOp = (TextView) view.findViewById(R.id.desc_op_tv);
        descOp.setOnClickListener(this);
    }

    public CollapsibleTextView(Context context) {
        this(context, null);
    }

    public final void setDesc(CharSequence charSequence, BufferType bufferType) {
        desc.setText(charSequence, bufferType);
        mState = COLLAPSIBLE_STATE_SPREAD;
        requestLayout();
    }

    @Override
    public void onClick(View v) {
        flag = false;
        requestLayout();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        if (!flag) {
            flag = true;
            if (desc.getLineCount() <= DEFAULT_MAX_LINE_COUNT) {
                mState = COLLAPSIBLE_STATE_NONE;
                descOp.setVisibility(View.GONE);
                desc.setMaxLines(DEFAULT_MAX_LINE_COUNT + 1);
            } else {
                post(new InnerRunnable());
            }
        }
    }

    class InnerRunnable implements Runnable {
        @Override
        public void run() {
            if (mState == COLLAPSIBLE_STATE_SPREAD) {
                desc.setMaxLines(DEFAULT_MAX_LINE_COUNT);
                descOp.setVisibility(View.VISIBLE);
                descOp.setText(spread);
                mState = COLLAPSIBLE_STATE_SHRINKUP;
            } else if (mState == COLLAPSIBLE_STATE_SHRINKUP) {
                desc.setMaxLines(Integer.MAX_VALUE);
                descOp.setVisibility(View.VISIBLE);
                descOp.setText(shrinkup);
                mState = COLLAPSIBLE_STATE_SPREAD;
            }
        }
    }
}
 

效果圖：

程式碼工程：