Toast分析

声明：
【转自】https://cloud.tencent.com/developer/article/1035830

自定义Toast

1.自定义Toast相当于自己做了makeText()方法的工作
源码位置：frameworks/base/core/java/Android/widght/Toast.java
Toast#makeText()

/**
     * Make a standard toast to display using the specified looper.
     * If looper is null, Looper.myLooper() is used.
     * @hide
     */
    public static Toast makeText(@NonNull Context context, @Nullable Looper looper,
            @NonNull CharSequence text, @Duration int duration) {
        Toast result = new Toast(context, looper);

        LayoutInflater inflate = (LayoutInflater)
                context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = inflate.inflate(com.android.internal.R.layout.transient_notification, null);
        TextView tv = (TextView)v.findViewById(com.android.internal.R.id.message);
        tv.setText(text);

        result.mNextView = v;
        result.mDuration = duration;

        return result;
    }

2.show()方法中内容

灵魂三问

• 通过getService()怎么就获得一个INotificationManager对象？
• TN类是个什么鬼？
• 方法最后只有一个service.enqueueToast()，显示和隐藏在哪里？

public void show() {
        if (mNextView == null) {
            throw new RuntimeException("setView must have been called");
        }

        INotificationManager service = getService();
        String pkg = mContext.getOpPackageName();
        TN tn = mTN;
        tn.mNextView = mNextView;

        try {
            service.enqueueToast(pkg, tn, mDuration);
        } catch (RemoteException e) {
            // Empty
        }
    }